Lymphatic filariasis, also known as elephantiasis, is best known from dramatic photos of people with grossly enlarged or swollen arms and legs. The disease is caused by parasitic worms, including Wuchereria bancrofti, Brugia malayi, and B. timori, all transmitted by mosquitoes. Lymphatic filariasis currently affects 120 million people worldwide, and 40 million of these people are seriously diseased. When an infected female mosquito bites a person, she may inject the worm larvae, called microfilariae, into the blood. The microfilariae reproduce and spread throughout the bloodstream, where they can live for many years. Often disease symptoms do not appear until years after infection. As the parasites accumulate in the blood vessels, they can restrict circulation and cause fluid to build up in surrounding tissues. The most common, visible signs of infection are excessively enlarged arms, legs, genitalia, and breasts.
Progeria is caused by a single tiny defect in a child's genetic code, but it has devastating and life-changing consequences. On average, a child born with this disease will be dead by the age of 13. As they see their bodies fast forward through the normal process of ageing they develop striking physical symptoms, often including premature baldness, heart disease, thinning bones and arthritis. Progeria is extremely rare, there are only around 48 people living with it in the whole world. However, there is a family that has five children with the disease.
When two year-old Abys DeJesus grew dark, hairy patches on her face, doctors said she has a condition known as Human Werewolf Syndrome. The disease is called werewolf syndrome because people with it look like werewolves - except without the sharp teeth and claws. In Mexico, a large family of men had hair that covered their faces and upper bodies. Two brothers were even offered a part in the X-Files but they turned down the offer.
A large family simply known as the "blue people" lived in the hills around Troublesome Creek in Kentucky until the 1960s. They were the blue Fugates. Most of them lived past the age of 80, with no serious illness - just blue skin. The trait was passed on from generation to generation. People with this condition have blue, plum, indigo or almost purple skin. (Source)
People diagnosed with Pica have an insatiable urge to eat non-food substances like dirt, paper, glue and clay. Though it is believed to be linked with mineral deficiency, health experts have found no real cause and no cure for this disorder.
There are people out there who go to great lengths to avoid the sun. If they are caught in the sun, their skin will blister. Some of them have pain and blistering as soon as the sun touches their skin. Ok, so they're not actually vampires. They don't drink blood and sleep in coffins, but they do suffer from a rare disease that has vampire-like symptoms.
Alice in Wonderland syndrome (AIWS), or micropsia, is a disorienting neurological condition which affects human visual perception. Subjects perceive humans, parts of humans, animals, and inanimate objects as substantially smaller than in reality. Generally, the object perceived appears far away or extremely close at the same time. For example, a family pet, such as a dog, may appear the size of a mouse, or a normal car may look shrunk to scale. This leads to another name for the condition, Lilliput sight or Lilliputian hallucinations, named after the small people in Jonathan Swift's Gulliver's Travels. The condition is in terms of perception only; the mechanics of the eye are not affected, only the brain's interpretation of information passed from the eyes.
Blaschko's lines are an extremely rare and unexplained phenomenon of human anatomy first presented in 1901 by German dermatologist Alfred Blaschko. Neither a specific disease nor a predictable symptom of a disease, Blaschko's lines are an invisible pattern built into human DNA. Many inherited and acquired diseases of the skin or mucosa manifest themselves according to these patterns, creating the visual appearance of stripes. The cause of the stripes is thought to result from mosaicism; they do not correspond to nervous, muscular, or lymphatic systems. What makes them more remarkable is that they correspond quite closely from patient to patient, usually forming a "V" shape over the spine and "S" shapes over the chest, stomach, and sides.
It is a syndrome of mental depression and suicidal tendencies, in which the patient complains of having lost everything: possessions, part of or entire body, often believing that he or she has died and is a walking corpse. This delusion is usually expanded to the degree that the patient might claim that he can smell his own rotting flesh and feel worms crawling through his skin. The latter phenomenon is a recurring experience of people chronically deprived of sleep or suffering amphetamine/cocaine psychosis. Paradoxically, being "dead" often gives the patient the nation of being immortal.
The main characteristic is that patients are extremely startled by an unexpected noise or sight. It's not just twitching when someone sneaks up behind you. Patients with this disorder flail their arms, cry out and repeat words. First identified in some of Maine's lumberjacks of French-Canadian origin, the odd reflex has been identified in other parts of the world, too.