List of extraordinary diseases and conditions

This article provides a list of extraordinary, outstanding, or extremely rare diseases, disorders and medical conditions.

Congenital

 * Conjoined twins: whose bodies are joined in utero.


 * 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. A notable case is Lakshmi Tatma who was born with 4 arms and 4 legs; but this was not true polymelia but a case of ischiopagus Siamese twinning where one twin's head had disappeared during development. In polycephaly there are more than one head, though no further 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.


 * Monochromacy: "Total color blindness", is a complete inability to distinguish colors.

Infectious or parasitic

 * 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 have mistaken human penises for their preys.

Other

 * Elephantiasis: A disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs, male genitals and female breasts. In some cases, the disease can cause certain body parts, such as the scrotum, to swell to the size of a basketball. Neurofibromatosis can give overlapping symptoms (see elephant man).


 * Less common forms of phobias include anthophobia (fear of flowers), gephyrophobia (fear of bridges) and tetraphobia (fear of the number 4).


 * 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).




 * Death from laughter: Possible explanations includes infarction of the pons and medulla oblongata in the brain, which may cause pathological laughter.


 * 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.


 * 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.


 * 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.