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This article provides a list of diseases, disorders and medical conditions with unusual or unique causes, presentations, symptoms or treatments.
- Congenital insensitivity to pain: Chronic condition with inability to feel physical pain. Other sensation is otherwise normal. Children with this condition often suffer oral cavity damage both in and around the oral cavity (such as having bitten off the tip of their tongue) or fractures to bones.
- Complete androgen insensitivity syndrome: People with this condition are generally girls or women with normal female bodies by external appearance, but still have internal testes, and 46,XY karyotypes.
- True hermaphroditism: Having both ovarian and testicular tissue. There may be an ovary on one side and a testis on the other, but more commonly one or both gonads is an ovotestis containing both types of tissue. External genitalia are often ambiguous.
- Chimerism: Having two or more different populations of genetically distinct cells. The likelihood of the condition is increased if the child was created via in vitro fertilization.
- Severe combined immunodeficiency: It is also known as the "bubble boy" disease because its victims are extremely vulnerable to infectious diseases and must live in a completely sterile environment.
- Supernumerary body part: Growth of an additional part of the body. It includes polymelia: having more than the usual number of limbs. In polycephaly there are more than one head, though no more than two-headedness has been confirmed in humans. Other forms are diphallia (two penises) and uterus didelphys (double uterus, often with double vagina as well).
- Sirenomelia: Alternatively known as mermaid syndrome. It is a very rare deformity in which the legs are fused together, giving the appearance of a mermaid's tail.
- Ectopia cordis: The heart protrudes outside the chest.
- Situs inversus: The major visceral organs are reversed or mirrored from their normal positions. The normal arrangement is known as situs solitus. In other rare cases, in a condition known as situs ambiguus or heterotaxy, situs cannot be determined.
- Hypermobility: Having joints that stretch farther than is normal. It gives a natural advantage for contortionists.
- Progeria: Early aging. An extremely rare disorder in with symptoms resembling aspects of aging are manifested at an early age.
- Myostatin mutation: Results in muscle hypertrophy, recently reported in a German boy, who has got twice the muscle mass of children in his age and can lift weights that some adults would find challenging.
- Some forms of mutations in opioid receptors, which are the bodily effector targets for opiates and opioids such as heroin and morphine, have resulted in constant receptor activation.
- Trimethylaminuria (fish odor syndrome): Inability to break down trimethylamine, resulting in its accumulation and release in the person's sweat, urine, and breath, giving off a strong fishy odor or strong body odor.
Infectious or parasiticEdit
- Encephalitis lethargica: An atypical form of encephalitis whose last epidemic ended in 1926, leaving some victims in a statue-like condition, speechless and motionless. Three decades later some victims were brought back to life with treatment with levodopa, although the effect was temporary.
- Guinea worm disease: A parasitic worm disease, with the worm (between 2 and 3 feet long) burrowing into the deep connective tissues or adjacent to long bones or joints of the extremities. The only treatment has been to catch the worm once it emerges through the skin and wrap the live worm around a piece of gauze or a stick to extract it from the body. This long, painful process can take up to a month. 
- Candiru: A parasitic freshwater catfish that swims into the gill openings of other aquatic species, where it feeds on its prey's blood, lodging itself in place with its spines. In extremely rare cases candirus mistake human penises for their preys, and must be surgically removed. 
- Necrotizing fasciitis, commonly known as flesh-eating disease, is a bacterial infection of the deeper layers of skin and subcutaneous tissues, rapidly spreading across the fascial plane. The only first-line treatment is aggressive surgical debridement (removal of infected tissue) or amputation of the limb.
- Kuru: An incurable degenerative brain disease and a form of prion disease, believed by some to have spread easily and rapidly in the Fore people due to their endocannibalistic funeral practices, in which relatives consumed the deceased. 
- Death from laughter: Possible explanations include infarction of the pons and medulla oblongata in the brain, which may cause pathological laughter.
- Anterograde amnesia: Loss of memory of what happens after the event that caused it, in rare cases with normal intelligence and perceptual ability, yet with complete inability to remember or learn anything new. Its counterpart is retrograde amnesia, i.e. inability to recall events that occurred before the development of amnesia.
- Less common forms of phobias include anthophobia (fear of flowers), gephyrophobia (fear of bridges) and hexakosioihexekontahexaphobia (fear of the number 666).
- Some forms of paraphilias may be considered as disorders, e.g. autassassinophilia (attraction to putting oneself in highly hazardous situations), biastophilia (attraction to assault and rape) and vorarephilia (attraction to eating or being eaten by others; usually swallowed whole, in one piece).
- A small minority of people with Tourette syndrome exhibit coprolalia (involuntary swearing or utterance of obscene words) and/or copropraxia (involuntarily performing obscene or forbidden gestures).
- Savant syndrome: A rare condition in which persons with developmental disorders (including autism spectrum disorders) have one or more areas of expertise, ability or brilliance that are in contrast with the individual's overall limitations. The definition is disputed.
- Sleep sex: A form of parasomnia (similar to sleepwalking) that causes people to engage in sexual acts while they are asleep.
- Pica: Involving appetite for substances largely non-nutritive e.g. clay, coal, soil, feces, chalk, paper, soap, mucus, ash, gum etc.
- Motion blindness: Inability to see motion. Such people instead are only able to gauge movement in frames, making it e.g. hard to cross the street because cars appear up the street and then suddenly close, without ever seeming to occupy the intervening space.
- Prosopagnosia (face blindness): Inability to recognize faces.
- Alice in Wonderland syndrome: Sufferers may experience micropsia, macropsia, and/or size distortion of other sensory modalities.
- Genital retraction syndrome: A condition in which an individual is overcome with the belief that his/her external genitals—or also, in females, breasts—are retracting into the body, shrinking, or in some male cases, may be imminently removed or disappear. A penis panic is a mass hysteria event or panic in which male members of a population suddenly experience this belief.
- Cotard delusion: Holding a delusional belief of being dead, not existing, be putrefying or having blood or internal organs lost.
- Cataplexy: Sudden and transient episodes of loss of muscle tone, possibly total collapse, triggered by strong emotions such as exhilaration, anger, fear, surprise, orgasm, awe, embarrassment, and laughter. It is more prevalent in people with narcolepsy, which is extreme tiredness and possibly falling asleep during inappropriate times, such as at work or school.
- Aquagenic pruritus: Water allergy. Presents as a severe, intense, prickling-like epidermal itching evoked by contact with water.
- Persistent genital arousal disorder: Spontaneous and persistent genital arousal, with or without orgasm or genital engorgement. Orgasm can sometimes provide temporary relief, but within hours the symptoms return.
- Hypertrichosis: Hair density or length beyond the accepted limits of normal. More extensive cases of hypertrichosis have been called werewolf syndrome.
- Epidermodysplasia verruciformis: An extremely rare skin disorder, resulting in the growth of scaly macules and papules, particularly on the hands and feet, potentially making the victim appear like a tree. 
- ↑ "Colour Blindness." Tiresias.org. Accessed September 29, 2006.
- ↑ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
- ↑ [http://www.aegis.org/news/ct/2004/CT040611.html One Strong Tyke: Gene mutation in muscular boy may hold disease clues. Chicago Tribune - June 24, 2004
- ↑ Schuelke M, Wagner K, Stolz L, Hübner C, Riebel T, Kömen W, Braun T, Tobin J, Lee S (2004). "Myostatin mutation associated with gross muscle hypertrophy in a child". N Engl J Med 350 (26): 2682–8. doi:10.1056/NEJMoa040933. PMID 15215484.
- ↑ Befort K, Zilliox C, Filliol D, Yue S, Kieffer BL (June 1999). "Constitutive activation of the delta opioid receptor by mutations in transmembrane domains III and VII". J. Biol. Chem. 274 (26): 18574–81. PMID 10373467.
- ↑ Uniformed Services University of the Health Sciences, "Dracunculiasis", Tropical Medicine Central Resource, http://www.isradiology.org/tropical_deseases/tmcr/chapter27/intro.htm, retrieved 2008-07-15
- ↑ The Carter Center, "Guinea Worm Eradication Program", The Carter Center, http://www.cartercenter.org/health/guinea_worm/index.html, retrieved 2008-07-15
- ↑ Dr. Anoar Samad, "Candiru inside the urethra" translated page at web.archive, untranslated
- ↑ Wadsworth JD, Joiner S, Linehan JM, et al (March 2008). "Kuru prions and sporadic Creutzfeldt-Jakob disease prions have equivalent transmission properties in transgenic and wild-type mice". Proc. Natl. Acad. Sci. U.S.A. 105 (10): 3885–90. doi:10.1073/pnas.0800190105. PMC 2268835. PMID 18316717. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=18316717.
- ↑ Diamond JM (1997). Guns, germs, and steel: the fates of human societies. New York: W.W. Norton. pp. p. 208. ISBN 0-393-03891-2.
- ↑ Gondim, FA; Parks BJ, Cruz-Flores S et al. (December 2001). ""Fou rire prodromique" as the presentation of pontine ischaemia secondary to vertebrobasilar stenosis". Journal of Neurology, Neurosurgery, and Psychiatry 71 (6): 802–804. doi:10.1136/jnnp.71.6.802. PMC 1737630. PMID 11723208.
- ↑ Di Gennaro G, Grammaldo LG, Quarato PP, Esposito V, Mascia A, Sparano A, Meldolesi GN, Picardi A. Severe amnesia following bilateral medial temporal lobe damage occurring on two distinct occasions. Neurol Sci. 2006 Jun;27(2):129–33.
- ↑ Lisa Downing (Tuesday, June 08, 2004). "On the limits of sexual ethics: The phenomenology of autassassinophilia". Sexuality & Culture, Springer, New York. http://www.springerlink.com/content/ffpqwly85tdx1c1a/. Retrieved 2009-03-19.
- ↑ Money, J. (1984). Paraphilias: Phenomenology and classification. American Journal of Psychotherapy, 38, 164-178.
- ↑ Brundage, Sandy (July 31, 2002). "Fetish Confessions". The Wave Magazine 2 (15). http://www.thewavemag.com/pagegen.php?articleid=22026&pagename=article. Retrieved 2007-04-30.
- ↑ Schapiro NA. "Dude, you don't have Tourette's:" Tourette's syndrome, beyond the tics. Pediatr Nurs. 2002 May–Jun;28(3):243–6, 249–53. PMID 12087644 Full text (free registration required).
- ↑ Howard Hughes Medical Institute: The Strange Symptoms of Blindness to Motion by Geoffrey Montgomery. Retrieved on May 17,2009
- ↑ 18.0 18.1 Foreign Accents, Alien Hands and Other Medical Oddities Wall Street Journal DECEMBER 30, 2008
- ↑ Freedberg, et. al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0071380760.
- ↑ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. ISBN 0721629210.
- ↑ thehumanmarvels.com > WEREWOLF SYNDROME - Hypertrichosis Retrieved on may 16, 2009
- ↑ The man who looks like a tree | Metro.co.uk
- ↑ My Shocking Story: Half Man Half Tree. Discovery Channel.