Diseases and illnesses iceberg

Diseases and illnesses iceberg is an iceberg chart topic. On r/IcebergCharts, the highest-scoring available chart on it, "The Diseases and Illnesses Iceberg (volume 1)", was posted by u/bluesheepreasoning on 18 August 2021 and had about 723 upvotes when it was collected. A text version, "Ultimate Diseases Illnesses and Medical Conditions" by 500 CIGARETTES, is hosted on IcebergThreads, where it had 1,276 views as of 29 October 2026.

Entries reflect the chart authors' choices and are not verified fact.

"The Diseases and Illnesses Iceberg (volume 1)" by u/bluesheepreasoning (18 August 2021)

Tiers

Tiers and entries from the IcebergThreads version. Notes after a dash are shortened from the author's explanations.

Extremely common and/or most well-known

• Acne – Usually harmless "zits" that form on the face, chest and body when foreign bodies enter the pores in the skin. Risk factors can include stress, sweat, medications, dietary factors, or age, since acne…
• ADHD – Attention Deficit/Hyperactivity Disorder is another extremely common neuropsychological condition present from childhood onward, characterised by a short attention span, difficulty sitting still,…
• Allergies – The body's immune response to things it mistakenly considers a threat, including certain types of food, medication, or naturally occurring substances like pollen or nickel. Usually distressing rather…
• Alzheimer's disease – A common, severe, terminal form of dementia, as well as one of the leading causes of deaths worldwide.
• Anemia – Low red blood cell counts and iron deficiency in the blood. Anemia can have various causes, some more or less serious, but is easy to distinguish due to extreme fatigue, a pallid appearance,…
• Arthritis – An autoimmune disease that inflames and damages the joints, causing slow movement, chronic joint pain and trouble moving or completing daily tasks. While it is commonly associated with old age,…
• Asthma – Chronic, obstructive inflammatory disease of the lungs and airways, causing pus to build up in the airways during episodes (especially when certain triggers such as animal dander, dust or pollen are…
• Autism – Autism Spectrum Disorder, or simply autism, is a neuropsychological disorder present from childhood. Autistic people will see the world a little differently than people without autism; we will be…
• Bone fractures – Broken bones due to injury.
• Brain cancer – Tumor cell disease located in the brain, followed by symptoms of headaches, seizures, fainting, breathlessness, weakness, nausea, vomiting and mood swings. Even non-cancerous tumours of the brain can…
• Cerebral palsy – Neurological movement-related disorder present from childhood onward, usually due to a traumatic brain injury in infancy. Those with cerebral palsy may struggle with proper movement, verbal speech,…
• Chickenpox – Similarly to smallpox, but still existent and less lethal, it is a highly contagious disease brought on by the varicella-zoster virus, causing an itchy rash all over the body, sometimes even with…
• Cholera – Epidemically contagious dangerous bacterial infection of the digestive tract with Vibrio cholerae bacteria, transmitted through drinking unsanitary water, characterized among others by severe…
• Colon cancer – Tumor cell disease of the colon. Symptoms will include profuse rectal bleeding, rapid weight loss, loss of appetite, diarrhea, tarry stools, changes in bowel habits and abdominal cramping.
• Colourblindness – An X-chromosome gene mutation which interferes with certain light and colour-detecting cones in the eyes, making some of them non-functional or even completely nonexistent. There are multiple types…
• Common cold – A common, usually harmless viral infection of the upper respiratory tract, leading to coughing, sneezing, excess nasal mucus, high temperatures, and more. Usually goes away on its own within a week…
• COVID-19 – A type of coronavirus said to have originated from Wuhan, China, which led to a global pandemic in the years 2020-2022. Its symptoms, depending on the severity, are essentially those of the flu,…
• Depression – Major Depressive Disorder is a very common mental illness characterised by low mood, prolonged sadness, loss of interest in once enjoyable activities, changes in appetite or sleeping patterns,…
• Diabetes – Diabetes mellitus is an extremely common autoimmune condition that entails a lack of produced insulin to lower the blood sugar levels (type 1 diabetes) or an outright immunity to insulin paired with…
• Ebola – Extremely highly lethal strand of Ebolavirus, classified as a Class 4 risk by the World Health Organization. Also known as the Ebola Hemorrhagic Fever, it is a disease common especially in African…
• Eczema – Skin disorder marked by symptoms of dry, itchy skin and rashes. People with egzema are also more prone to having or developing asthma.
• Edema a.k.a. dropsy – Fluid buildup in the tissue. Can happen for many reasons, including overhydration, alcohol/drug usage, disease, etc. Leads to swelling. Most common in the hands and feet, but can be lethal if it…
• Epilepsy – A neurological condition characterized by reoccurring seizures. It usually comes into being due to poorly-wired brain circuitry or a traumatic head injury.
• Epistaxis – Nosebleed, or a bleeding from the nose.
• Generalized Anxiety Disorder – Anxiety disorders fall under an umbrella term of mental disorders which entail heightened fear, worrying, hypervigilance and even feelings of guilt. In more severe cases, the suffering may develop…
• H1N1 – A variant of influenza virus that can be connected to the so-called "Spanish flu", also infecting pigs and birds (avian and swine flu variants). Caused a short pandemic in the years 2009-2010.
• Hantavirus – A pulmonological virus spread by rodents, which usually does not cause any symptoms for them, but it does for humans - and the symptoms are those of severe pneumonia. Treatment includes prolonged…
• Hay fever – Allergic rhinitis, also known as hay fever, is a harmless (unless you also have asthma) yet debilitating and distressing series of allergic reactions to pollen in the air during periods of tree…
• Headlice – Small, wingless, parasitic insects that infest the human scalp and cause itching with their bites.
• Hepatitis – Viral inflammation of the liver. The type of hepatitis in question depends on how the virus was acquired - through contaminated food or water (type A), transmitted sexually (type B) or through…
• HIV/AIDS – The Human Immunodeficiency Virus, or HIV, is a virus transmitted through sexual or blood contact, which, while lifelong, can be managed with medications and inhibitors, leading to a normal life…
• Influenza a.k.a. "the flu" – A highly contagious yet common viral infection preventable with a non-mandatory vaccine. The disease entails the classic symptoms of a cold, but more severe, plus other symptoms such as chest pains…
• Insomnia – Difficulty falling or staying asleep. Factors can be various: illness, anxiety, medications, etc. May be eased with melatonin.
• Lactose intolerance – An inability to digest lactose due to a lack of the enzyme lactase in the bowels. It does not cause harm to the gastrointestinal tract and is generally a relatively harmless condition in the long…
• Leukemia – Cancer of the blood, that originates in the bone marrow from excessive immature leukocyte (white blood cell) growth. The immature white blood cells kill off red blood cells, normal white blood cells…
• Lung cancer – Carcinoma of the lungs - the most lethal kind of cancer. Biggest risk factor is, obviously, smoking.
• Malaria – Parasitic disease usually found in third-world countries, caused by the parasite Plasmodium, carried through the bite of an infected mosquito.
• Measles – Vaccine-prevntable viral disease characterized by rashes and patches on the skin. Typically most dangerous to very young children and the elderly, otherwise highly treatable in adults.
• Migraines – Moderate to severe headaches that manifest on one side of the head. They can last anywhere between 4 and 72 hours. Frequent migraines 8 out of 10 times are paired with nausea and vomiting. A migraine…
• Monkeypox a.k.a. Mpox – Viral disease brought on by a virus of the genus Orthopoxvirus, that causes a bumpy, itchy skin rash, sometimes mucuousal, but also a fever, headaches and muscle pains. A global outbreak of Mpox did…
• Multiple Sclerosis – Autoimmune disease characterized by the body's immune system attacking the nerve cells and neurons of the brain. Chronic and lifelong, but those with it can live a normal life when adapted and…
• Myocardial infarction a.k.a heart attack – Sudden, but usually not unprompted cessation of flow of oxygen-rich blood into the heart, which, in turn, "suffocates" the heart and leads to its sudden stop. A heart attack is always a…
• Ovarian cancer – Cancer of the ovaries, as opposed to the uterus. Both types of cancer may, however, cause infertility. Women with Polyendocrine Metabolic Ovarian Syndrome (PMOS) are at a higher risk for developing…
• Pertussis a.k.a. whooping cough – Bacterial infection of the respiratory tract, by Bordetella pertussis bacteria. Its less formal name derives from the sound an infected person makes while trying to breathe, which sounds vaguely like…
• Phobias – Extreme, oftentimes irrational fears of specific things, in ways that may be classified as an anxiety disorder. Everyone is afraid of something, but phobias will cause extreme avoidance of the…
• Pneumonia – Inflammation of the lungs. In most cases, it is brought on by Streptococcus pneumoniae bacteria, and entails chest pains, coughing (either dry or producing yellow, green or brown phlegm), sweating,…
• Polio – Short for Poliomyelitis, and is also known as Heine-Medin Disease. A viral infection found usually in children in third world countries, obtained by consuming food/water contaminated with human…
• Prostate cancer – Cancer of the prostate.
• Rabies – Viral infection of the brain spread through the bites of infected mammals such as dogs, foxes, raccoons or bats. Rabies is the most lethal disease on planet Earth, and can only be stopped before…
• Sepsis – An out-of-control bodily reaction to an infection, also known as "blood poisoning" - always a life-threatening medical emergency.
• Skin cancer – Cancer of the skin, whereby excess sunlight on the beach may increase the risk of, if not directly cause it.
• Smallpox (no longer exists) – A viral disease characterized by itchy, pus-filled skin bumps, which haunted humanity from ancient times well until 1979, when it was eradicated completely. The first disease to have been completely…
• Social Anxiety Disorder – An anxiety disorder marked by extreme fear of social situations especially when surrounded by people, sensitivity to rejection and other people's reactions, isolation, avoidance of social…
• Staph food poisoning – Foodborne illness from consuming unrefrigerated food contaminated with toxins produced by Staphylococcus bacteria - usually goes away with proper treatment and rest, and is treated like any other…
• Strep throat – "Strep" as in Streptococcus bacteria. Bacterial infection of the throat, treated, like most bacterial infections, with antibiotics.
• Stroke – A sudden interruption of blood flow to the brain that leads to braincell death. A stroke may also be a sudden gush of blood to the brain from a burst vessel (hemorrhagic stroke). Always a…
• Tetanus – A bacterial infection of an open wound or cut on the skin by Clostridium tetani bacteria found in earth, soil, sand and animal feces. The bacteria then produce a toxin that paralyzes the nerves and…
• Trisomy 21 a.k.a. Down Syndrome – A genetic mutation entailing excess genetic material on chromosome 21. As an effect, people with the condition will often have small upturned eyes, an stumpy neck, short height, a flat nose bridge,…
• Tuberculosis – Mycobacterium tuberculosis bacteria can attack virtually almost any organ and cause a form of tuberculosis in it, but the one we are speaking of here is the most common form of tuberculosis, which…
• Uterine cancer – Cancer of the uterus. Women who have never been pregnant or who have endometriosis are at an increased risk for it.

Common and/or well-known

• Albinism – Genetically inherited condition characterised by a lack of melanin in the skin, hence white skin and red or purple eyes. Such individuals are also most prone to sunburn and other skin conditions.
• ALS a.k.a. Lou Gehrig's disease – Amyotrophic lateral sclerosis is a rare, yet well-known terminal neurodegenerative disease which causes muscle wasting, mobility issues, speech issues, difficulty swallowing and, in about 15% of…
• Anaphylaxis – Also known as "anaphylactic shock", it is a severe allergic reaction to an allergen, that causes a drastic drop in blood pressure, followed by seizures, convulsions, vomiting, skin rashes, urinary…
• Aneurysm – A bulge in a weakened artery wall that usually isn't painful, but may lead to internal bleeding if untreated.
• Anorexia nervosa – The word "anorexia" on its own is the medical term for loss of appetite. However, anorexia nervosa is an eating disorder most common in adolescent girls, though boys can have it too. It is marked by…
• Appendicitis – Inflammation of the appendix due to bacteria, intrusion of feces, toxins or other causes. Always a life-threatening medical emergency requiring surgery. Even more life-threatening, should the…
• Astrovirus – Common virus that causes mild diarrhea in children and usually goes away with proper treatment.
• Athlete's foot – A type of foot fungus that causes itching, dry skin, scaling and redness.
• Avian flu – Bird-specific variant of influenza virus, spread to humans through contact with infected birds.
• Bipolar disorder – Manic Depressive Disorder is a psychotic mental illness which brings on periods of extreme clinical depression, followed by periods of mania (high elation and energy), with perhaps some periods of…
• Bone cancer – Malignant tumour in the bones.
• Bronchitis – Usually viral infection and inflammation of the bronchial tubes inside the lungs. Symptoms pretty much coincide with pneumonia, but milder. The key difference between bronchitis and pneumonia is that…
• Bubonic plague – The most common form of any plague, caused by the bacterium Yersinia pestis, spread through the bite of an infected flea, usually one that caught it from first biting an infected rat. Also known as…
• Bulimia nervosa – Another common eating disorders among adolescent girls, which can also, albeit less commonly, affect boys. As opposed to anorexia, individuals with bulimia will go all out eating, throwing themselves…
• Bunions – Bony growths on the side of the foot that push the big toe into all the other toes.
• Carpal tunnel syndrome – Cramping wrist pain caused by prologed exhaustion of the hand by writing, typing, drawing, playing instruments or video games, etc.
• Cataracts – A clouded lens of the eye, causing blurred and "foggy" vision. Usually caused by excess sunlight (especially in people with bright eyes), but also can be tied into age, diabetes, weight, genetics,…
• Celiac disease – Autoimmune disease characterized by a moderate to severe allergy to all gluten products due to antibodies mistakenly attacking the parts of the colon that help with gluten digestion.
• Conjoined twins – Twins whose bodies have been fused together in the womb due to a genetic defect. The most famous case happened in 1811 with the two boys Chang and Eng, born in Thailand - hence why the name "Siamese…
• Conjunctivitis – Also known as "pink eye". A reddening (pinkening?) and swelling of the eye due to irritants such as bacteria, viruses, smoke, dirt, pollution, allergies or even STDs.
• Cowpox – Viral disease caused by the cowpox virus, usually due to infection from a cow. It results in dotty lesions all over the body, which are usually swollen, inflamed and painful.
• Croup – Common childhood viral infection, rarely lethal, leading to a "barking" cough.
• Dengue fever – Subtropical viral disease spread through the bite of infected mosquitos. The majority of cases are asymptomatic, but other cases invite muscle pains, severe headaches and rashes. Can be fatal, but is…
• Diphteria – Respiratory infection caused by Corynebacterium diphtheriae. Preventable with a vaccine, leads to a barking cough, a sore throat, a raspy voice and a dense grey pseudomembrane covering the tonsils…
• Dysentery – Bacterial infection due to drinking contaminated water, usually when it is contaminated with human feces. Lethal if untreated, leads to diarrhea with blood.
• Dyslexia – Learning disability which causes problems with reading, while maintaining a normal or even very high intelligence.
• E. coli – Escherichia coli bacteria are the "good" kind of bacteria when they serve as gut flora in the human colon and help with digestion. However, consuming unsanitary food and poor sanitation in places…
• Erectile dysfunction – The inability to get or keep an erection long enough to have proper sex. Also known as impotence. Usually treated with viagra.
• Fifth disease – Common childhood infection with parvovirus B19, characterised by a reddish rash, especially on the cheeks, something akin to chickenpox.
• Gangrene – A type of bacterial tissue death due to lack of blood flow and oxygen. The skin around the infected part will turn black or red (as a sign of rotting flesh) and, if untreated, can be quickly fatal.
• Gender dysphoria – The notion of being dissatisfied with one's assigned gender at birth, wishing to change it through gender reassignment surgery. People with this disorder are known as transgender. Though not all…
• Glaucoma – Intense pressure inside the eyeball(s) that slowly damages the optic nerve. May lead to vision loss if untreated.
• Gonorrhea – A sexually-transmitted disease (STD) caused by the bacterium Neisseria gonorrhoeae or gonococcus, leading to an inflammation of the genitals, reproductive system and urinary tract.
• Herpes – A (usually) sexually-transmitted viral disease with class-A symptoms of blister-like sores near the genitals and/or mouth, sometimes paired with symptoms similar to those of the flu. However, not all…
• HPV – Human papillomavirus, the most common STD worldwide, can also be spread from wounds and skin-to-skin contact.
• Hypertension – High blood pressure. Can be caused by stress, medications, altitudes, comorbidities, etc. When the blood pressure is too high, it usually manifests itself in symptoms such as headaches, vertigo,…
• Hypoglycaemia – Low blood sugar.
• Jaundice – Not so much as a disease, as more of a symptom of a more grave underlying condition. Jaundice is a yellowing of the skin and eyes with bilirubin, implying liver or gallbladder failure from conditions…
• Laryngitis – Bacterial inflammation of the larynx.
• Leptospirosis – Blood infection caused by Leptospira bacteria.
• Liver cancer – Cancer of the liver. Those especially susceptible to it are individuals who very frequently consume alcohol, even more so if irresponsibly.
• Liver cirrhosis – Permanent scarring and damage to the liver due to chronic liver disease, excessive fats, hepatitis, or, very frequently, copious alcohol consumption.
• Lumbago – Lower back pain.
• Lymphoma – Cancer of the lymph nodes. Similarly to leukemia, it is a blood cancer that comes into being when white blood cells grow out of proportions, but unlike leukemia, which always originates in the bone…
• Mumps – Vaccine-preventable viral disease that usually affects children, causing the neck and face to swell and leading to fever, malaise, headaches and fatigue.
• Myopia – Near-sightedness.
• Nephrolithiasis a.k.a. kidney stones – Hardened minerals and salts formed inside the kidneys, leading to back pains, nausea, vomiting and painful urination. One of the worst pains to experience, aside from giving birth, is passing a…
• Obsessive-Compulsive Disorder – Obsessive-Compulsive Disorder is an anxiety disorder with symptoms of recurring intrusive thoughts and, in many cases, compulsive behaviours meant to stimulate oneself from the fear-inducing images…
• Osteoporosis – Condition that gradually decreases bone mass, causing bones to become frail and brittle.
• Other coronaviruses (SARS-CoV1, etc.) – Large group of respiratory viruses which infect humans and animals both.
• Pancreatic cancer – Cancer of the pancreas. Has an 92% mortality rate due to how quickly it spreads. It is also very hard to detect at its earliest stages because up until stage 3-4, it is usually asymptomatic. Symptoms…
• Panic attacks – Sudden episodes of extreme fear, with physical symptoms such as a feeling of breathlessness, hyperventilating, racing heart rates, sweating, shaking, cold hands, cold flashes, hot flashes, chest…
• Paraplegia – Varying degrees of paralysis or lack of sensory functions in the lower extremities, most commonly due to a spinal injury. Paraplegic individuals may or may not be wheelchair-bound.
• Parkinson's disease – Discovered and described by James Parkinson in 1817, this is a neurological disease which typically manifests in old age. Unlike what many claim, Parkinson's is not a death sentence, but it does…
• Pharyngitis – Inflammation of the throat. Can be bacterial, viral or fungal, and usually appears as a co-exisiting symptom of other diseases, from the common cold down to pneumonia.
• Polyendocrine Metabolic Ovarian Syndrome a.k.a. Polycystic Ovary Syndrome – Hormonal condition of the ovaries due to an overproduction of androgens, leading to cysts in the ovaries, infertility, missed or irregular periods and more facial/body hair.
• Post-Traumatic Stress Disorder – After a horrific event from the past such as war, sexual assault and/or rape, bullying, a near-death experience, loss of a loved one, or others, the brain may shield itself from potential future…
• Psoriasis – Lifelong autoimmune dermatological condition characterised by pink, purple or red patches of dry and/or itchy skin all over the body. While it has no cure, it can be eased with medications and creams.
• Rubella – A viral disease causing a spotty rash all over the skin, usually a childhood disease. Also known as German measles.
• Salmonella – A type of bacterial food poisoning, caused by Salmonella bacteria, leading to 40-degree fevers, vomiting, nausea, diarrhea, abdominal pains, and generally more severe symptoms of food poisoning.
• Scarlet fever
• Schizophrenia – A psychotic mental illness which, in most cases, sets in in adulthood. The affected will experience periods of auditory and visual hallucinations, fear, paranoia, derealization and detachment from…
• Shingles – Viral infection characterised by a painful skin rash. Caused by the same virus that causes chickenpox.
• Sixth disease – Also known as "Roseola". Childhood viral infection with a strand of Herpesvirus known as Human herpesvirus 6 or Human herpesvirus 7. Generally highly treatable with a good prognosis, but…
• Stockholm syndrome – A neuropsychological phenomenon that sees a person become emotionally and psychologically attached to their captor or abuser.
• Stomach ulcers – Small bleeding sores formed on the stomach lining by Helicobacter pylori infections. A common risk factor for ulcers is stress and high levels of stomach acids.
• Stye – Painful bump on the eyelid from a blocked oil gland.
• Swine flu – A variant of the influenza virus which mainly affects pigs, but can spread to humans through droplet contact with infected pigs (e.g. when a pig sneezes on them).
• Syphilis – Sexually-transmitted bacterial disease caused by an infection with the bacterium Treponema pallidum. Symptoms include itchy white or grey warts around the genitals or anus, swollen lymph nodes,…
• Tachycardia – Condition that causes a higher-than-average heartbeat.
• Tapeworms – Large parasitic worms that infest the colon after ingesting their larvae or eggs in contaminated or poorly cooked food, usually meat. They will lead to rapid weight loss, diarrhea, vomiting, nausea,…
• Tinnitus – Common, distressing condition marked by hearing sound, especially ringing in the ears, when no external sound is present. While "normal tinnitus" is experienced by nearly everyone in a completely…
• Tonsilitis – Bacterial (but sometimes also viral) inflammation of the tonsils, causing a painful soreness in the throat and potential vocal loss. Treated, depending on severity, by surgically removing the…
• Tourette's syndrome – Mental disorder characterised by uncontrollable tics, or behaviours such as making sudden noises, twitches or movements in order to satisfy an urge. In extreme cases, these tics may involve sudden…
• Typhoid fever – Life-threatening gut infection with Salmonella typhi bacteria, found in contaminated food or water.
• Typhus – Bacterial disease carried through the bite of head- and body lice infected with Rickettsia typhi or Rickettsia prowazekii. May also be spread by fleas and chiggers carrying these bacteria. Causes…
• Vitiligo – A harmless, but potentially psychologically distressing skin condition marked by white discolourations forming all over the body, in varying patterns due to the body's autoimmune reaction mistakenly…
• Yellow fever – Typically short-lasting African viral disease spread by infected mosquitoes, which, for about 15% of people, after the symptoms have seceded for a day, they will return, making the skin turn yellow…

Somewhat common and/or somewhat known

• Acute radiation sickness – Self-explanatory: strong radiation from substances like uranium, radium, etc. causes the body to become sick and, in the long run, damages the brain. It also causes cancer. Mass cases of acute…
• Antisocial Personality Disorder – Personality disorder characterised by a lack of or very few emotions, little to no empathy, a tendency to be selfish and manipulative, aggression and recklessness. People with this disorder are…
• Astigmatism – Eyesight-related refractive condition that appears when the cornea or the lens of the eye has mismatched curves, causing the surface of the eye to be oval-shaped rather than perfectly spherical. As a…
• Ataxia – Movement-related disorder of the central nervous system, impairing movement, often causing stiffness and wobbliness while walking or performing daily tasks.
• Azoospermia – Lack of sperm in ejaculation, relatively treatable.
• Binge-eating disorder – Lesser known, but still prevalent and harmful eating disorder. The person affected will, much like bulimics, throw themselves on binges of eating food, but instead of purging it as it happens for…
• Borderline Personality Disorder – A particular personality disorder with a name deriving from the fact that it is on the borderline between neurosis (a mild mental disorder that doesn't entail a loss of touch with reality, such as…
• Borreliosis a.k.a. Lyme disease – Disease spread through the bite of a tick infected with Borrelia burgdorferi. Symptoms include a bull's eye rash, flu-like symptoms and headaches. While it usually takes two weeks to recover,…
• Botulism – Rare, but potentially lethal disease obtained from consuming poorly home-canned foods, infected with a type of bacteria that produces the Botulinum toxin, which leads to nerve paralysis.…
• Bradycardia – Condition that causes a lower-than-average heartbeat.
• Candidiasis a.k.a. thrush a.k.a. yeast infection – An overgrowth of yeast fungi of the candida genus. In most cases, yeast infections are associated with genital infections, or non-STD fungal infections of the genitals, but they can appear in other…
• Chikunguya – Dengue-like tropical viral disease present mostly in Asia and Africa, spread by mosquito bites. It usually lasts between 3 to 7 days and is very rarely fatal.
• Chlamydia – Sexually-transmitted bacterial disease causing genital pain, discharge, and, more often than not, an infection of the urinary tract.
• Clinodactyly – Bone malformation that causes a small hook-like limpness to develop at the end of a finger. Common especially in people with Down Syndrome, but can affect virtually anyone.
• Crimean-Congo Hemmorrhagic Fever – Viral tickborne disease with symptoms similar to Ebola, but a much lower fatality rate at 10-40%.
• Cryptosporidiosis – Infection with Cryptosporidium protozoans, transmitted through contaminated water or pigeons and their feces. Symptoms include watery diarrhea.
• Cystic fibrosis a.k.a. mucoviscidosis – Autosomal dominant disorder which produces large quantities of mucuous in the lungs and other organs, leading to breathing obstructions, fatty stool and poor growth. Also known as mucoviscidosis.
• DID/OSDD – Dissociative Identity Disorder or Other Specified Dissociative Disorders are very rare and always only manifest in people with severe, repeated childhood trauma, but they are both rare disorders,…
• Dirofilariasis (dogs) – Parasitic infection with worms of the genus Dirofilaria, which mostly affects dogs and other members of the canid family, treated with certain antiparasitic drugs.
• Dyscalculia – What can essentially be described as dyslexia, but with mathemathics.
• Dysgraphia – Like dyslexia, except instead of reading, the person in question will struggle with writing, despite normal intelligence.
• Endometriosis – Systemic inflammatory disease of the female reproductive system wherein endometrial cells similar to those which line the inside of the uterus grow outside of the uterus, causing pelvic pain and…
• Felinosis a.k.a. cat scratch fever – Human infection with Bartonella henselae, which occurs from the scratch or bite of a cat, or sometimes when a cat licks an open wound, as these bacteria are said to derive from the saliva of cats.…
• Fetal alcohol syndrome – The result of consuming alcohol while pregnant. People born with fetal alcohol syndrome may have stunted growth, mental handicap and distorted facial features. Don't drink if you're pregnant.
• Gastritis – Inflammation of the stomach lining upon infection with Helicobacter pylori, the same bacteria that cause stomach ulcers. Treated by antibiotics or antacids, but in severe cases, the stomach lining…
• Giardiasis – Parasitic infection with giardia protozoans, common especially in children and travelers. Causes fatty, sticky diarrhea and abdominal cramping.
• Gingivitis – Usually mild and harmless bacterial inflammation of the gums. When untreated, however, it can make way for periodontitis.
• Haemophilia
• Hyperopia – Far-sightedness.
• Infectious mononucleosis a.k.a "mono" – Usually, though not always, caused by the Epstein-Barr virus (from the genus Herpesvirus), mono is spread through saliva, hence why it's also called the "kissing disease". It causes a severely sore…
• Leprosy
• Lordosis a.k.a. swayback – A forward curve in the lumbar spine.
• Lupus – Autoimmune condition, causing the body's immune system to mistakenly attack healthy organ tissue and tissue lining, leading, very often so, to rashes and skin ulceration.
• Melanoma – Malignant tumor, typically on the skin, caused by a tumor cell among melanocytes (the cells responsible for producing melanin in the skin). Typically recognisable as a large mole that keeps…
• Meningitis – Infection and inflammation of the protective membranes of the brain. Can be viral, bacterial or fungal, but is life-threatening if untreated regardless of the cause.
• Myelitis – Inflammation of the spinal cord - classified as neurological due to how it disrupts brain function by having an impact on the neurons.
• Narcissistic Personality Disorder – NPD does not have a clear-cut-and-dry cause, but can be attributed to genetics or excess adoration or, on the contrary, excessive criticism as a child - that, however, doesn't have to be the case.…
• Neuroma – Benign nerve tumour that most often forms in the foot (Morton's neuroma). Cancerous nerve tumours usually have other names.
• Norovirus a.k.a. Norwalk virus a.k.a. winter vomiting disease – Viral infection of the gastrointestinal tract spread through the fecal-oral route, arousing symptoms of watery (non-bloody) diarrhea, vomiting, nausea, weakness, fever and chills. Recovery typically…
• Pinworms – Small white worms which sometimes infest the human colon and anus, leading to itching in the rectal area. They only affect humans and are usually mostly harmless, but extremely unpleasant. They are…
• Pyeleonephritis – A kidney infection, usually due to a bacterial infection. It entails painful urination, lower abdominal pain, flank tenderness, frequent urination, nausea, vomiting, fever and more. Diagnosed with…
• Ringworm – Fungal infection of the skin (not an actual worm). Causes itchy patches that can look round.
• Rotavirus – A highly infectious type of gut virus which leads to diarrhea, vomiting, abdominal pains and more.
• Scabies – Also known as the "Seven-Year Itch", scabies is a contagious skin disease caused by being bitten by mites.
• Scoliosis – Common disorder characterized by an abnormal curvature of the spine. I have it myself, and can testify I have uneven shoulders and chronic back pain.
• Scurvy – Disease brought on by a critically low amount of vitamin C intake, characterised by bleeding gums, weakness and receding muscles. Was most common among sailors back in the old days, whose only form…
• Toxoplasmosis – Parasitic infection with Toxoplasma gondii protozoans, acquired either through poorly-cooked food or through contact with cat feces. These protozoans live in the digestive systems of house cats.…
• Urinary tract infection – Bacterial inflammation of the urinary tract, which, depending on when it is determined and treated, may affect the urinary tract, bladder and then the kidneys - the last being far more dangerous and…
• West Nile virus – Mosquito-transmitted flavivirus which causes West Nile fever - additionally, the same genus of viruses causes Zika, dengue and yellow fever.
• Whiplash – Neck injury that is caused by a too-sudden backwards jerk.
• Zika virus

Less common and/or lesser known

• Alopecia areata – An autoimmune condition which makes the hair fall out in some or all areas of the body. In some cases, people with the disease may not even have eyelashes. However, it does not affect the health or…
• Amblyopia – "Lazy eye", or a weakness in vision and movement in one eye.
• Anthrax – An infection with Bacillus anthracis through skin absorption, consumption or inhalation. The first onset is a painless, coal-black ulcer on the skin, but further symptoms will invite vomiting,…
• Aplastic anemia – Rare and serious bone marrow disease that results in low blood cell count. Differs from regular anemia in the sense that while normal anemia only affects red blood cell counts, aplastic anemia…
• Asbestosis – Chronic lung disease from prolonged exposure to asbestos; asbestos poisoning of the lungs.
• Atherosclerosis
• Avoidant Personality Disorder – Those with Avoidant Personality Disorder are chronically shy, perpetually anxious and mistrustful, and tend to isolate themselves and avoid being noticed in order to steer clear of any situation that…
• Balanitis – Inflammation of the glans penis, which can affect men of all ages. If the foreskin is also affected, this is referred to as balanoposthitis.
• Café-au-lait spots – From the French words meaning "coffee with milk" due to their creamy brown colour like coffee with milk, they are medium-sized brown melanin birthmarks on the skin. Some, though not all people, might…
• Campylobacter infection – The name essentially meaning "curved bacteria" (as the bacteria themselves literally possess a curved shape), campylobacter infections usually cause a diarrhoeal disease known as campylobacteriosis.…
• Chagas disease – Parasitic tropical infection of the blood by Trypanosoma cruzi parasites, from exposure to the urine or feces of an infected American triatomite bug (kissing bug). This insect is almost exclusive to…
• Chilblains – Small, itchy, reddened patches that develop on the skin after being exposed to cold temperatures. They usually do not require treatment and will go away on their own.
• Cluster headache – Severe headache that centers around an eye. Different from migraines, rarer and affects more men than it does women.
• Crabs – Pubic lice. They are usually transmitted through sexual contact and appear in the pubic hair, but sometimes even in chest hair or eyelashes. They may bite, cause genital itching, or even stain…
• Crohn's disease – Chronic inflammatory disease of the gastrointestinal tract, usually the colon.
• Dermatographic urticaria – Skin disorder that causes red lines and welts when the skin is scratched. The affected can literally scratch out words in their skin that come out in red welts. It is not infectious or dangerous to…
• Emphysema – Condition causing breathlessness from the alveoli being excessively enlarged by air.
• Encephalitis – Inflammation of the brain.
• Ergotism – Long-term effect of ergot poisoning, or poisoning with certain secretions of Claviceps purpurea ergot fungi that infect rye and grains. Earlier stages involve convulsions, seizures, vomiting and…
• Fibromyalgia – Rheumatological syndrome punctured with widespread muscle pains, chronic fatigue, depression, movement issues and sensitivity to touch (which increases the muscle pain). It doesn't affect the…
• GERD – Gastroesophegal Reflux Disease. Acid reflux, which irritates the throat and leads to, among others, heartburn and nausea.
• Hernia – Parts of an organ protruding through the muscle wall due to an injury (sometimes from straining or lifting something much too heavy for the body to take).
• Hypernatremia – Excessive sodium concentrations in the blood.
• Hyphema – Blood accumulation in the iris due to an eye injury.
• IBS – Irritable Bowel Syndrome is a chronic disease of the upper digestive tract (the colon) that contracts the muscles. It is less grave and more easily manageable than Crohn's disease. More often than…
• Impetigo – Also known as "school sores", this is a short-term, rather harmless if unpleasant bacterial disease characterised by itchy sores forming on the superficial skin of young children due to certain…
• Intersex – Intersex people are born with both male and female anatomy. Meaning, a person may look female on the outside, but have XY chromosomes or mostly male internal anatomy and sex organs - or vice versa.…
• Interstitial cystisis – Also known as Bladder Pain Syndrome (BPS), it is a common chronic inflammatory bladder disease with the same symptoms as a UTI, only not bacterial.
• Japanese encephalitis – Parasitic disease spread to humans through the bite of an infected mosquito - symptomatic cases are rare and the fatality rate is about 30%.
• Keloids – Raised scars on areas where the wound has healed. Oftentimes found on poorly-maintained piercings.
• Lassa fever – A hemorrhagic viral fever with a special risk in African countries (first discovered in 1959 in Lassa, Nigeria) spread through African rats and mice infected with the Lassa virus by consuming food…
• Listeriosis – Infection through consuming food contaminated with Listeria bacteria. Nearly everyone infected with literiosis is hospitalised, and the death rate, while relatively low for what could be, is higher…
• Marburg virus disease – Hemorrhagic fever brought on by the genus Marburg marburgvirus, a virus first discovered in Marburg, Germany. Symptoms and lethality similar to ebola.
• Misophonia – "Hatred of sounds", marked by irritation or even aggression in response to certain sounds like pen clicking, chewing or loud breathing. Anyone can be irritated by these sounds, but people with…
• Myalgic Encephalopathy/Chronic Fatigue Syndrome – Exactly what it sounds like. Being constantly tired despite being well-rested. May also be paired with insomnia, exercise intolerance and brain fog.
• Myiasis (DO NOT LOOK AT THE PICTURES) – Infestation of tissue by maggots (fly larvae). Maybe I just have a weak stomach, but I don't think I'll be the same person after seeing the pictures...
• Narcolepsy – Chronic neurological condition which leads to sudden, episodic sleeping and increased fatigue. The sleep episodes can happen even when a person is standing up or engaging in an activity.
• Neuroblastoma – Cancer in certain types of nerve tissue, such as the adrenal glands, chest, neck, spine or head. It primarily affects children under 5 years old and is the cause of 15% of cancer deaths in children.
• Nyctalopia – Night blindness, difficulties seeing in dim lighting.
• Obsessive-Compulsive Personality Disorder – Personality disorder marked by extreme perfectionism, a need to control one's surroundings, sensitivity to criticism, inability to compromise, doubt and a fixation on certain beliefs. Different from…
• Osgood-Schlatter Disease – Condition wherein the tendon of the knee pushes against the shinbone. Most common form of growth pains in adolescents between the ages of 11-14, usually goes away with time.
• Paranoid Personality Disorder – A particular personality disorder that entails, as may already have been guessed, chronic mistrust and fearfulness of others, believing everyone may be out to get them.
• Periodontitis – Unlike gingivitis, which, for the most part, is relatively harmless, periodontitis is a serious gum disease which recedes the gums and affects tooth recession in the process. May lead to tooth loss…
• Peripheral neuropathy – Damage to the nerves outside of the brain or spinal cord. Most commonly affected are the limbs, causing severe pain and motor issues.
• Peritonitis – Inflammation of the abdominal wall lining (peritoneum) after an injury or infection. May require surgery or antibiotics depending on the cause. Symptoms usually present themselves in the form of…
• Prader-Willi Syndrome – Chromosomal mutation which causes the sufferer to have an enormous, difficult to satisfy appetite for food. Sometimes, if denied food, people with Prader-Willi may go on to eat out of the trash or…
• Prosopagnosia – "Face blindness". Difficulty, if not inability to remember and recognise people's faces.
• Psittacosis a.k.a parrot fever / ornithosis – Infection of birds and humans with Chlamydia psittaci, most commonly parrots and domestic birds, but also pigeons, sparrows, ducks, doves and other non-domesticated birds. Symptoms manifest as severe…
• Restless leg syndrome – Long-term condition causing an increased desire to move the legs (esp. at night) due to pain and discomfort, followed by daytime sleepiness, low energy and mood swings. More common in older people.
• Rickets
• Rinderpest (cattle) (no longer exists) – The second disease to ever be fully wiped out (after smallpox), rinderpest was a highly infectious viral disease of cattle and pigs, spread through air and water, with extremely high mortality rates.…
• River blindness – Parasitic infection spread to humans through repeated bites of blackflies infected with Onchocerca volvulus worms, most of which tend to reside in rivers used by the people for bathing, swimming and,…
• Rocky Mountain spotted fever – Much like Lyme disease, Rocky Mountain spotted fever is an infection spread by an infected parasitic tick. They are nonetheless two different diseases which stem from different types of bacteria that…
• Sickle-cell anemia – Genetically inherited blood disorder affecting the shape of red blood cells and shaping them like sickles (crescent-shaped rather than round, like in the case of healthy blood cells). Crescent-shaped…
• SIDS – Sudden Infant Death Syndrome is exactly what it sounds like: a sudden, unexpected death of an infant under the age of 12 months, which, until then, appeared completely healthy.
• Strabismus – Eye misalignment, or when one eye is turned in a different direction than the other.
• Swimmer's itch – Caused by a waterborne parasite that may reside in snails, that can penetrate the skin and cause itching. This parasite is typically found in shallow waters. It is not transmittable, not contagious…
• Tendonitis – Inflammation of the tendon in the arm, foot, hand or leg from a sudden injury or excess pressure on the muscles, especially during physical activity. Treated with ice, rest and physical therapy. A…
• Teratoma – A type of germ cell tumor, which may be cancerous or benign, that contains immature or premature tissue, such as hair, bone, muscle, or even teeth. As known as they may be, they are statistically…
• Toxic shock syndrome – Very rare but life-threatening complication of certain bacteria-produced toxins, 10 times more lethal when caused by Streptococcus bacteria than Staphylococcus bacteria. Associated with surgery…
• Wilson's disease – Genetically inherited disease which excessive amounts of copper are generated in the body.
• Yersiniosis – Gastrointestinal infection with bacteria of the Yersinia genus, caught by consuming raw or undercooked pork.

Uncommon and/or more obscure

• Acanthocytosis – Acanthocytosis is the result of severe liver disease, or sometimes other conditions like anorexia nervosa or certain genetic diseases. It is when a large number of the body's red blood cells have…
• African sleeping sickness – Disease transmitted through the bite of a Tsetse fly. It is known as the sleeping sickness due to one of its primary symptoms being constant, heavy fatigue. If untreated, it can be lethal.
• Alice in Wonderland Syndrome – A neurological disorder, also known as dysmetropsia, causing episodes of auditory and visual hallucinations such as perceiving objects as bigger, smaller, closer up or further down than they actually…
• Alien hand syndrome – The hand acting like it has a mind of its own. This disorder is caused by lesions in the corpus callosum and/or the left frontal lobe of the brain. The sufferer will lose control of their hand,…
• Angiostrongyliasis a.k.a. "rat lungworm disease" – A disease caused by infection with Angiostrongylus parasites. It is quite well-known because it's been shown to infect snails and slugs, which, in turn, can pass it on to other organisms.
• Arachnoiditis – Inflammation around the nerve roots of the spine.
• Aspergilliosis – Fungal infection of the lungs (and very rarely the skin) by breathing in a type of common mould of the Aspergillus genus. Interestingly enough, most people will not be affected by it, and the ones…
• Avoidant/Restrictive Food Intake Disorder – ARFID is an eating disorder that isn't as commonly known as anorexia, bulimia or BED. It is, basically, exactly what it says in the name: avoiding foods that look or smell displeasing (for example…
• Babesiosis – Disease spread through the bite of a tick infected with the parasite Babesia.
• Beriberi – A chronic and more severe form of thiamine (vitamin B1) deficiency. Beriberi is divided into two categories: "dry" (affecting movement-related muscles) and "wet" (affecting the heart). Either can be…
• Boils – Hard, sore, pus-filled lumps on the skin from bacteria entering the pores of hair follicles and inflaming them. Usually they go away on their own.
• Botryomycosis – Large, pus-filled bumps on the skin, most frequently from Staphylococcus aureus infections.
• Brucellosis – Bacterial disease that mostly affects animals such as cattle, sheep, pigs and dogs, but can be transferred to humans upon consuming raw animal products or unpasteurized milk, or contact with the…
• BSE a.k.a. Mad Cow Disease – Bovine spongiform encephalopathy is an invariably fatal, untreatable neurodegenerative prion disease of cattle - cows with this disease will have difficulty walking and display abnormal behaviour,…
• Burning mouth syndrome – A seemingly out of nowhere condition which causes a sudden burning sensation in the mouth and tongue.
• Chancroid – Sexually transmitted genital ulcer caused by Haemophilus ducreyi.
• Coal miner's lung disease – Charred black lungs from inhaling dust and debris from working at or being in coal mines for long periods of time. Can be life-threatening.
• Congenital analgesia – A rare congenital inability to feel any physical pain. While it doesn't affect the health on its own, it is nonetheless an extremely dangerous and life-threatening condition, solely because of how…
• Creutzfeld-Jakob Disease – A degenerative brain disease caused by a mutated protein known as a prion. There is no cure, as it is always lethal, as prion diseases go. While it isn't necessarily the same as Mad Cow Disease, it…
• Cyclosporiasis – Intestinal infection with the Cyclospora cayetanensis parasite, usually through the fecal-oral route. Though the infection isn't usually life-threatening, it will cause symptoms such as vomiting,…
• Dependent Personality Disorder – Personality disorder that, as the name suggests, causes a person to become overly dependent on their relationships, to the point of excess clinginess, fear of rejection, difficulty disagreeing so as…
• Dermatillomania – Obsessive picking at the skin, sometimes to the point of bleeding. What causes this disorder is not entirely clear, but it often goes hand-in-hand with Obsessive-Compulsive Disorder.
• Dyspraxia – Movement-imparing disorder causing increased clumsiness and difficulty walking or standing, often paired with dyslexia, dyscalculia and dysgraphia. As in all of these conditions, it does not affect…
• Ehlers-Danlos syndrome – Overly stretchy skin and hypermobile joints due to genetically predisposed faulty tissue connection. 13 different types of EDS exist, but almost all share the symptoms of loose joints that are prone…
• Elephantiasis – Parasitic disease usually found in the tropical and subtropical regions, carried through the bite of an infected mosquito. When said mosquito then bites a human, it can cause extremely painful…
• Folie à deux – From the French words translated roughly as "insanity for two". When a mentally stable person takes on the symptoms of a close loved one who suffers from a psychotic disorder. It doesn't imply…
• Hashimoto's disease a.k.a. Hashimoto's thyroiditis – Comes into fruition when lymphocytes mistakenly start attacking the thyroid gland, inflaming and degenerating it. Because the thyroid is responsible for hormone secretion, it may lead to loss of some…
• Hemicrania continua – Headache that affects one side of the head, always on one side. Unlike migraines, which vary, and tend to come and go, hemicrania rarely or never goes away, but can be managed with pain medication.…
• Histrionic Personality Disorder – Essentially the opposite of Avoidant Personality Disorder. People with HPD strive to be noticed. They will act provocatively and dramatically, be sensitive to all rejection, interpret personal…
• Huntington's chorea – A neurodegenerative inherited brain disease, which gradually kills off the braincells. "Chorea" refers to the uncontrollable movements that are part of it. It is not the disease itself that's fatal,…
• Hydrocephalus – Hydrocephalus is an enlarging of the head due to excess buildup of cerebrospinal fluid in the ventricles of the brain. Usually seen in newborns.
• Legionnaire's disease – Serious pneumonia (lung inflammation) from the aspiration of Legionella bacteria from water droplets in hot tubs, swimming pools, lakes and other water bodies into the lungs. This may also happen…
• Leishmaniasis – Parasitic disease transmitted through bites of sandflies, especially in tropical and subtropical regions. Characterized by ulcers on the skin, can be deadly if untreated.
• Locked-in syndrome – One of the most terrifying conditions to exist, it is a state wherein a comatose patient is aware they are in a coma but can do nothing about it. Such people will be immobile beyond moving around…
• Ménière's disease – Rare inner ear condition that causes vertigo, ringing in the ears, hearing loss and ear congestion - discovered in 1861 by French physician Prosper Ménière,.
• Munchausen Syndrome – Individuals with Munchausen syndrome will fake being sick, or make themselves sick, for the purpose of attention. In some cases, they may make someone else, possibly a loved one, sick by (for…
• Murray Valley encephalitis virus – Serious but rare viral infection with a virus native to Australia, New Zealand and Papua New Guinea.
• Myelodysplasia – Blood cancer that lowers the amount of produced blood cells in the bone marrow. Sometimes referred to as preleukemia.
• Myxomatosis (rabbits) – Viral disease that affects rabbits, caused by the Myxoma virus. Rabbits affected with this disease will have swollen eyes, swollen genitals, ocular and nasal discharge, respiratory issues, etc. In…
• New Brunswick neurological syndrome – Very self-explanatory full name: New Brunswick neurological syndrome of unknown cause. However, it has been classified as a potential new neurodegenerative disease causing paralysis, memory failure,…
• Paraphelic Disorders – Sexual interest in objects, situations, or individuals that are atypical that include distress, impairment in functioning, and the desire to act on them with a non-consenting party. Different from a…
• Polydactyly – Having more than 5 fingers on one hand.
• POTS – Postural Orthostatic Tachycardia Syndrome entails a sudden drastic increase in heart rate while standing up from sitting down, especially when standing up too fast. It frequently results in fainting…
• Progeria a.k.a. Hutchinson-Gilford Syndrome a.k.a. "Benjamin Button disease" – Extremely rare (1 in 18 million) uncurable genetic disease that causes a child's body to age rapidly and show symptoms of old age before inevitably dying at age 13-15. Named after the 2008 movie "The…
• Schizoid Personality Disorder – A personality disorder marked by a lack of emotional attachment, social withdrawal, lack of interest in forming personal connections and apathy towards other people in general, under the premise of…
• Schizotypal Personality Disorder – Personality disorder that shows itself through the person not knowing how interpersonal relationships work and having very few close relationships, possessing and displaying odd beliefs and greatly…
• Situs inversus – Having major internal organs "facing the wrong way", in the opposite direction of how they are usually allocated in the human body. It usually doesn't cause any problems.
• Synesthesia – A neurological phenomenon which links unrelated senses to other factors - for example, one might hear a song and immediately associate it with a colour. As an autistic person with synesthesia, I can…
• Toxic encephalopathy – Caused by long-term exposure to neurotoxins like mercury or manganese, or certain prescription drugs. Can permanently damage the brain.
• Trimethylaminuria a.k.a. "fish odour syndrome" – Strange condition that causes the affected's sweat, urine and other bodily fluids to reek of fish.
• Turner Syndrome – A genetic defect where a baby assigned female at birth is missing one or half of one X-chromosome. Girls and women with this disorder will often possess a short stature, a lack of defined female…
• Vibriosis – Disease caused by Vibrio bacteria infections, usually caught by exposing a wound to warm seawater. Brings about symptoms such as diarrhoea, vomiting, wound infections, ear infections and fever.
• Von Willebrand disease – Lifelong inherited bleeding condition where the blood does not clot properly due to changes in the gene responsible for the protein that helps blood clot, the von Willebrand factor. Symptoms don't…
• Wolff-Parkinson-White syndrome – Rare heart condition that will occasionally cause the heart to randomly begin having palpitations or beating extremely fast. In more severe cases, the symptoms can last for days. Usually is not…
• Xenomelia – Body integrity disorder, or xenomelia, is a neuropsychological phenomenon wherein the person in question is uncomfortable with the notion of being able-bodied and will amputate healthy limbs, blind…
• Zollinger-Ellison Syndrome

Very uncommon and/or very obscure

• Acromegaly – An overproduction of growth hormone in the midlife stage, causing enlarged feet, enlarged hands, obstructed airways, excess sweating and body odour as a result, large gaps between the teeth and…
• Alpha-gal syndrome – A severe allergy to red meat that derives from certain tick bites. Some ticks produce an enzyme known as Alpha-gal that, which enters the human bloodstream upon a bite, triggers an allergic reaction…
• Aphakia – Lack of a lens in one or both eyes.
• Aquagenic urticaria – Skin disorder which causes itchy rashes to cover the whole skin when it comes in contact with water. No cure is available, but treatment, so as to allow people with this disorder to bathe and…
• Baylisascariasis – Also known as the "raccoon roundworm", this disease is transmitted through raccoon feces, as raccoons are its definitive hosts. This is why steering clear of raccoons, not keeping them as pets and…
• Bell-clapper deformity – Testicles sitting horizontally instead of vertically due to a congenital malformation.
• Black hairy tongue – A frightening-looking, yet harmless condition that entails exactly what it says in the name: the tongue gaining a black, furry look due to, usually, poor oral hygiene, smoking, a soft food diet or…
• Blackwater fever – Rare yet life-threatening complication of malaria, which gets its name from the fact that those affected will rapidly pass a lot of dark-coloured urine. Other symptoms include high fevers, extreme…
• Bronchopulmonary dysplasia – This condition usually is diagnosed in prematurely-born babies which still require breathing support 28 days after birth. Babies with BPD will have very fragile lungs and display signs of wheezing…
• Brugada Syndrome – A genetic disease that causes frequent arrhythmias, seizures, and even fainting. It can be fatal, but normally they die during sleep or rest. The one who proposed this entry (PiglinMiguel) has a long…
• Cancrum oris a.k.a. noma (DO NOT LOOK AT THE PICTURES) – Gangrenous infection around the mouth, most common in the Subsaharan region of Africa known as the "Noma Belt". It mostly affects children aged 2-6 with poor oral hygiene, and has a high fatality…
• Chiggers – A species of parasitic fleas, usually red or orange in colour, that infest the human skin and may lay eggs underneath it, causing itching.
• Chronic Wasting Disease (deer) – Also known as "zombie deer disease", this is another transmissible spongiform encephalopathy which affects deer, especially when spread when deer come into contact with urine, feces and other excreta…
• Dracunculiasis a.k.a. Guinea worm – Skin infection with the "Guinea worm" Dracunculus medinensis, contracted by consuming water infected with its larvae and fleas. Death only occurs in about 1% of cases, but with how rare the disease…
• Dysautonomia – Condition that causes the autonomous nerves to stop working properly, leading to fainting, low heartbeat and malnutrition.
• Dysthymia – Milder, yet much longer-lasting depression.
• Exploding Head Syndrome – Despite its name, this condition is a harmless, if frightening, sleeping disorder, marked by episodes of sudden, loud auditory hallucinations before falling asleep or waking up.
• Fatal familial insomnia – An extremely rare neurodegenerative inherited disease caused by a misfolded protein (prion) in the brain. The disease is typically divided into four stages: the first being progressive insomnia which…
• Foreign accent syndrome – Exactly what it sounds like. Strange condition and phenomenon that causes the affected to speak their own language with a different accent than their country of origin.
• Gigantism – Prepubescent form of acromegaly, causing a child to grow extremely tall.
• Granulomatous amoebic encephalitis – Very rare infection with free-living amoeba of the genus Acanthoamoeba, Balamuthia or Sappina, leading to seizures, headaches, fever and even personality changes. The survival rate is very low, but…
• Guillain-Barré syndrome – Rare autoimmune condition wherein the body's immune system mistakenly attacks its peripheral nerves, leading to muscle numbness, stiffness and mobility issues.
• Harlequin ichtyosis (DO NOT LOOK AT THE PICTURES) – A rare genetic disorder. Babies with this disorder are born prematurely with thick, hard skin that forms diamond-shaped plates all over their bodies, separated by red fissures, which added together…
• Hirschsprung's disease – When certain nerves are missing from a newborn's colorectal area, leading to vomiting and constipation in the baby, this is Hirschsprung's disease. It is more common in boys than girls, and is…
• Hyperthymesia – Extremely good memory. So extremely good, in fact, these people will be able to remember every day of their life in vivid detail beginning from a certain point in time. Only 62 cases have been…
• Kala-azar – Visceral leishmaniasis, also known as kala-azar (Hindu for "black fever") is the most severe form of leishmaniasis, that manifests when the parasite that causes leishmaniasis migrates to the liver,…
• Klinefelter syndrome – Boys with Klinefelter syndrome are born with an extra X chromosome, making their chromosomal structure XXY. They are usually very tall and thin, bear more feminine features such as rounder hips,…
• Kuru – Also known as the "Laughing Disease" due to its late stages before death involving episodes of uncontrollable laughter, Kuru is a rare prion disease transmitted through cannibalism. This is one of…
• Maple syrup urine disease – Genetically transmitted disease which involves an inability in the body to break down and digest certain proteins, leading to blood in the urine and a sweet smell to boot, making it look and smell…
• Mass psychogenic illness – Also known as mass hysteria, it is when a large group of people starts displaying symptoms of an illness out of hysteria/anxiety, but does not actually suffer from any illness. One example could be…
• Melioidosis – An infection with Burkholderia pseudomallei bacteria from contaminated soil or water. Those with diabetes are at especially high risk for it. Symptoms coincide with pneumonia.
• Möbius syndrome – Congenital facial paralysis, inability to move the face or make facial expressions.
• Naegleriasis a.k.a. "brain-eating amoeba" – Naegleria fowleri are tiny, free-living amoeba of the eukaryote domain, which, due to their thermophilic (heat-loving) properties, tend to reside in warm waters of lakes, hot springs, warm water…
• Necrotizing fasciitis a.k.a. "flesh-eating disease"
• Nipah virus – A viral zoonotic infection spread most commonly through fruit bats and pigs, with an extremely high mortality rate that lies somewhere between 50% and 75%.
• Oligodactyly – Having less than 5 fingers on one hand.
• Pica – Unusual eating disorder classified by an appetite for inedible materials which may or may not include metal, wood chips, paint chips, grass, plastic, or other foreign material that is not considered…
• Polymelia – Having extra limbs (eg. three legs instead of two).
• Progressive vaccinia
• Q fever – A disease commonly mistaken for brucellosis, because it, too, can be caught through consuming the byproducts of infected animals such as unpasteurized milk or certain meats, but also from the contact…
• Septicaemic plague – The third of the three types of plague caused by Yersinia pestis bacteria, which is always fatal, but only if untreated, and is otherwise quite treatable. May lead to, among others, diarrhea,…
• Syndenham's chorea a.k.a. St. Vitus' dance – A childhood-onset neurological autoimmune condition characterised by uncontrollable jerking and twitching movements around the arms, face, legs and other parts of the body after a childhood infection…
• Syringomyelia – A cyst (syrinx) that develops in the spinal cord. Removed surgically.
• Tay-Sachs Disease – Genetic disorder characterised by an intolerance to fats, inability to break down fats by the body, a slow killing off of braincells and nerves in the brain and spinal cord, and a very premature…
• Trichotillomania – Like dermatillomania, but instead of picking at their skin, the person will obsessively pull out their hair. Also often goes hand in hand with Obsessive-Compulsive Disorder.
• Tularemia a.k.a. "rabbit fever" – Zoonotic infection with Francisella tularensis, leading to skin ulceration, breathing difficulties, fever and swollen lymph nodes. Generally caught from bites of deer flies, contact with infected…

Extremely uncommon and/or extremely obscure

• Alpers disease – Rare terminal genetic disorder which leads to dementia, liver failure and seizures.
• CADASIL – Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy is a hereditary genetic (autosomal dominant) stroke disorder with symptoms that involve minor strokes,…
• Capgras delusion – Psychotic delusion which makes the affected believe their partner, friend, relative or other loved one has been "replaced" by an identical imposter or someone wearing their skin, and that they are…
• Copremesis – Fecal vomiting. Usually a symptom of conditions such as gastrocolic fistulae.
• Cri-du-Chat syndrome – "Cri du chat" is French for "cry of the cat", and the name derives from the fact, that newborns with this condition make crying noises that sound much like the meowing of a cat. This is a very rare…
• Cronkhite-Canada syndrome – Non-hereditary, sporadic disease that is characterised by multiple polyps in the gastrointestinal tract. It is idiopathic, meaning the cause is unknown.
• Ectrodactyly – Having almost no fingers, or only two on the hands and/or feet - "lobster claws"
• Evans syndrome – Autoimmune disease causing the body to mistakenly attack its own red blood cells, leading to anemia.
• Feline spongiform encephalopathy a.k.a. FSE (cats) – Invariably fatal neurodegenerative disease which affects cats, caused by the same agent which causes Mad Cow Disease in cows. Infected cats display symptoms classic to those of all other prion…
• Fountain syndrome – Genetically inherited condition leading to slowed mental and motor skills, deafness, skeletal defects and a coarse face with a full mouth.
• Galactosemia – Rare genetic metabolic disorder that disables the body from properly digesting the sugar galactose.
• Kawasaki Disease – Rare but serious rash in young children under five years old, with a 0.17% fatality rate if untreated. Discovered by Tomisaku Kawasaki. Very little is known about this disease, not even what causes…
• Kyphosis – An outward curve in the spine so severe, it produces a large hump on the back. It's what Quasimodo suffered from in "The Hunchback of Notre Dame".
• MSA a.k.a. Multiple System Atrophy a.k.a Shy-Drager syndrome – Rapidly progressing fatal neurodegenerative disease, more common in men than in women, with symptoms of parkinsonism and muscle stiffness, bringing about complications that may even include cardiac…
• Neurofibromatosis
• Patau syndrome
• Piebaldism
• Renal glycosuria – A genetically inherited condition that causes a large quantity of the body's contained blood sugar, even if it is at normal levels or even too low, to be excreted. It's also known as "diabetes…
• Scrapie (sheep) – Yet another fatal neurodegenerative prion disease, this time affecting sheep - the name "scrapie" is derived from the fact that sheep infected with scrapie will compulsively scrape against rocks,…
• Syndactyly – Two or more finger joints fused together.
• Witzelsucht – German for "joking addiction". It shows when a person will constantly make jokes at inappropriate times, in some cases sexual ones (hypersexuality). It can happen to anyone, but doing it too much or…
• Yaws – Chronic skin infection with Treponema pallidum bacteria, leading to large ulcers on the skin.

Ultra uncommon and/or ultra obscure

• Achondrogenesis – The most severe form of chondrodysplasia, resulting in an abnormally small body at birth and such bone malformations, it is always fatal. I wouldn't advise looking at the pictures.
• Adrenoleukodystrophy a.k.a. Lorenzo's oil disease – Genetic disease affecting the white matter in the brain and adrenal glands, that usually only affects men, because the gene is located on the X chromosome. The buildup of fatty acids caused by ALD in…
• Alkaptonuria a.k.a. "black urine disease" – Rare autosomal recessive disease wherein large quantities of so-called homogentsic acid and its oxidised form, alkapton, are excreted in the urine, giving it a dark, almost blackish colour.
• Anencephaly – A complete lack of a brain at birth due to folic acid deficiency during pregnancy.
• Anosognosia – The brain not recognising its own body's illness. A patient may be blind or paralysed and nevertheless still think everything is normal.
• Argyria – A skin condition where the skin discolours and turns silver, due to prolonged, excess contact with silver. It does not affect the health at all, though it can be a factor of shame and psychological…
• Auto-brewery syndrome – A very rare gastrointestinal disorder that turns consumed sugars and carbohydrates into ethanol instead of properly digesting them, resulting in the person quite literally getting drunk from eating…
• Canavan disease (variant 1) – A rare, fatal autosomal recessive neurological disease which kills off the braincells between the ages of 3 and 6 and diminishes the white matter in the brain. However, there is another variant of…
• Clinical lycanthropy
• Cotard delusion
• Cyclopia (DO NOT LOOK AT THE PICTURES)
• Epidermodysplasia verruciformis a.k.a. "Tree-Man Syndrome"
• Fibrodysplasia Ossificans Progressiva a.k.a. "Stone Man Disease"
• Fragile X syndrome
• Fournier gangrene (DO NOT LOOK AT THE PICTURES)
• Hendra virus
• Hypertrichosis a.k.a. Werewolf Syndrome
• Idiopathic intracranial hypertension
• Intermetamorphosis delusion
• Jumping Frenchmen of Maine syndrome
• Lima syndrome
• Marie Antoinette syndrome (women) a.k.a. Thomas Moore syndrome (men)
• Macroglossia
• Methemoglobinemia
• Mirror-touch synesthesia
• Morgellons disease
• Pentasomy X a.k.a. Pentachromacy a.k.a. 49, XXXXX
• Sirenomelia
• Stiff man syndrome
• Subacute sclerotising panencephalitis a.k.a. Dawson's disease

Exceptionally uncommon and/or exceptionally obscure

• Alexander Disease
• Boanthropy
• Conjoined triplets
• Diprosopus
• Encephalitis lethargica
• Eosinophilic Granulomatosis with Polyangiitis
• Extrapelvic endometriosis
• Fregoli delusion
• Ganser syndrome
• Gerstmann-Straussler-Scheinker Syndrome
• Goodpasture's syndrome
• Hallermann-Streiff Syndrome
• Heart cancer
• Jacobsen Syndrome
• Klüver–Bucy syndrome
• Mayer–Rokitansky–Küster–Hauser syndrome
• Pachydermoperiostosis
• Paris-Trousseau Syndrome
• Poland syndrome
• Reye's Syndrome
• Truman Show delusion
• Variably Protease-Sensitive Prionopathy
• XXXXY syndrome a.k.a. 49, XXXXY

See also

• Iceberg chart
• R/IcebergCharts
• Biology iceberg

Sources

• Featured Reddit chart: u/bluesheepreasoning. The Diseases and Illnesses Iceberg (volume 1). Reddit (r/IcebergCharts). 18 August 2021. Retrieved 29 October 2026.
• IcebergThreads version: 500 CIGARETTES. Ultimate Diseases Illnesses and Medical Conditions. IcebergThreads. 17 January 2026. Retrieved 29 October 2026.