1. Stone Man Syndrome
It’s called fibrodysplasia ossificans progressiva, or FOP. A mutation causes fibrous tissue to become ossified when it’s damaged. That means your joints will become permanently frozen in place. This is an extremely rare disease, and if you have it, you’ll know it. There’s no known cure for FOP today. However, in 1993, scientists discovered that squalamine, an extract from sharks may help in fighting FOP, but that has been put up for debate. The New York Times wrote an article about Harry Eastlack, perhaps the most well-known figure with FOP in modern day history.
[youtube http://www.youtube.com/watch?v=a5PuLIuEUVs&w=584&h=390%5D
2. Alice In Wonderland Syndrome
Alice In Wonderland Syndrome is a rare psychological disorder where the sufferers experience size distortion, increased or decreased volume of sound, and exaggerated perception. It happens in episodes and is very disorienting for the sufferer. AWIS happens when excess electrical activity causes abnormal blood flow into the area vision and the part of the brain that processes texture size and shape, which explains size distortion.
It is documented that AIWS is frequent with childhood, but people grow out of it (although some have reported to have the disorder well into their 70s). It also occurs if muscimol, a psychoactive alkaloid, is ingested.
[youtube http://www.youtube.com/watch?v=yBdx64LkZnU&w=584&h=390%5D
3. Water Allergy
Possibly the worst condition to exist, aquagenic urticaria, or “water allergy” is a painful skin reaction when it comes into contact with water. The pain can last from anywhere up to 20 to 120 minutes. Sweating even triggers a reaction and so, people with this condition avoid sweating or heat as much as possible.
[youtube http://www.youtube.com/watch?v=ddLr3vEaJww&w=584&h=390%5D
4. Lewandowsky-Lutz Dysplasia
Lewandowsky-Lutz dysplasia is a hereditary skin disorder with no known cure-all treatment. Doctors and scientists believe that it is caused by an ineffective immune system coupled with HPV.
The tree bark-like growths are actually warts and grows back “faster” once surgically removed, as stated by Dede Kosawa, also known as Tree Man.
[youtube http://www.youtube.com/watch?v=DStwXsmZ3OE&w=584&h=390%5D
5. Fish Odor Syndrome
Trimethylaminuria is an incredibly rare metabolic disorder, which causes a person to have a strong body odor that resembles fish.
The buildup and release of trimethylamine, which is excreted through sweat, urine and breath, is what creates this odor. This disorder is more common in women than men, but it is observed that there are no physical symptoms that accompany trimethylaminuria.
The first scientifically documented case of trimethylaminuria was in 1970, but it is believed that it has been a condition that has existed for centuries.
[youtube http://www.youtube.com/watch?v=vm6Q6IP5LAY&w=584&h=390%5D
6. Alien Hand Syndrome
It sounds like something out of science fiction or a horror tale — where a hand goes rogue and doesn’t do what you tell it to do.
The first case of alien hand syndrome (also known as anarchic hand) was documented in 1908 by a German neuro-psychiatrist named Kurt Goldstein. He observed the patient to have no control over her left arm, as if someone else were controlling it. This neurological disorder occurs in people who have had the two hemispheres of their brains surgically separated, or from having a stroke, and even having Creutzfeldt–Jakob disease (human form of Mad Cow Disease). The hand basically becomes autonomous and the person believes it has a will of its own. You can read more about it here.
[youtube http://www.youtube.com/watch?v=dIBBDuQrd-I&w=584&h=390%5D
7. Methemoglobinemia
Methemoglobinemia is a disorder that describes blood with an abnormally high concentration of methemoglobin — a bluish-brown hemoglobin that carries iron in the ferric state. This leads to reduced oxygen levels throughout the body, because red blood cells lose their ability to release oxygen to tissues. With methemoglobinemia, hypoxia — the deprivation of oxygen — of organs and tissue may occur.
[youtube http://www.youtube.com/watch?v=Md2vqARiMJs&w=584&h=390%5D
8. Cotard Delusion
Also known as Walking Corpse Syndrome, patients suffering from this mental disorder believe that they are dead. Sometimes, they are of the belief that they possess immortality. This syndrome is documented to occur in three stages: Germination, blooming, and finally, chronic. Electroconvulsive therapy is cited to be most effective out of all of the treatments.
This syndrome was first described by Jules Cotard, in a lecture he gave in 1880.
[youtube http://www.youtube.com/watch?v=SLodoVzpZp0&w=584&h=390%5D
9. Parry–Romberg Syndrome
Parry–Romberg syndrome, or progressive hemifacial atrophy, is described as the progressive shrinkage and degeneration of the tissues beneath the skin, usually on one side of the face.
This syndrome is highly prevalent in women, but it is documented that this syndrome is an extremely rare neurocutaneous syndrome.
The disease results in the atrophying of skin and tissues beneath it, causing the mouth and nose to deviate towards the atrophied location.
Neurological, ocular and oral disorder accompany Parry–Romberg syndrome and it is appears to occur randomly and affects the left side of the face more than the right.
10. Cronkhite–Canada Syndrome
This rare syndrome is actually sporadic, meaning not hereditary, and the scientific community believes it to be an acquired disease.
Cronkhite–Canada syndrome seems to afflict mainly Japanese men and was discovered in 1955.
The syndrome begins off with polyps in the gastrointestinal tract, but quickly evolves, usually within months, and leads to extreme weight loss and edema — the swelling of organs.
11. Kleine–Levin Syndrome
Kleine–Levin syndrome is an extremely rare (one in a million) sleep disorder where the afflicted sleeps for days, or weeks on end. They also experience hypersexuality and hyperphagia (excessive hunger). KLS is, however, not life-threatening and appears to resolve itself as the afflicted ages. There is no known explanation as to why this happens, but doctors and scientists believe that the thalamus is responsible for this disorder.
[youtube http://www.youtube.com/watch?v=MYp7JdQqLfQ&w=584&h=390%5D
12. Morgellons Syndrome
Morgellons syndrome is a disorder where the sufferer believes that they are infested with insects or parasites, when in reality, they are not.
People with Morgellons syndrome experience itching, crawling, biting/stinging sensations with skin lesions. It is believed that Morgellons is a fixed belief; that is, a fixation.
[youtube http://www.youtube.com/watch?v=Mw2nwTPKjQ8&w=584&h=390%5D
13. Stendhal Syndrome
Stendhal syndrome was first documented with the French author, Henri-Marie Beyle, whose pseudonym was Stendhal. He described his experience in Florence in 1817, where he was so overwrought with emotion, he was “in a sort of ecstasy, from the idea of being in Florence, close to the great men whose tombs I had seen. Absorbed in the contemplation of sublime beauty… I reached the point where one encounters celestial sensations… Everything spoke so vividly to my soul. Ah, if I could only forget. I had palpitations of the heart, what in Berlin they call ‘nerves.’ Life was drained from me. I walked with the fear of falling. (Interfaces of Performance)” Its name, however, was given in 1979 by Italian psychiatrist Graziella Magherini.
It is a psychosomatic disorder that causes rapid heartbeat, confusion and even fainting when viewing art.
[youtube http://www.youtube.com/watch?v=fjc37cn8EUE&w=584&h=390%5D
14. Cyclic Vomiting Syndrome
Cyclic vomiting syndrome, or CVS, is characterized by attacks of severe nausea, vomiting, headaches and abdominal pain. It is documented that CVS is developed over childhood and has the chance of persisting into adult life.
Patients with CVS, on average, are 3-7 years old, and symptoms include vomiting up to six times in an hour. Episodes may happen every few days, weeks or months and for some, there are warning signs of an attack, ranging from hypersensitivity to fatigue.
15. Nail-Patella Syndrome
Nail–patella syndrome also called NPS is a genetic disorder that results in underdeveloped fingernails and kneecaps. The name is misleading in that it can also affect other regions of the body, namely the chest and hips. People with NPS may have pronounced deformities like limited motion of the elbows, severe scoliosis, and cervical ribs.
16. Charles Bonnet Syndrome
Charles Bonnet syndrome, or CBS, is characterized as highly complex visual hallucinations in patients suffering vision loss. Sufferers are generally mentally sound except that they hallucinate vivid faces. They are aware that these are hallucinations and not real. CBS affects people with visual impairments and patients with macular degeneration with glaucoma are most susceptible to CBS. 
