27 Rare and Mysterious Medical Conditions

FCAS is a rare, inherited disorder that affects how the body controls inflammation. It is characterized by episodes of rash, fever, and joint pain when the body is exposed to cold temperatures usually for an hour or longer.

Fatal Familial Insomnia is a very rare degenerative brain disorder characterized by insomnia that gets worse with time, eventually resulting in physical and mental deterioration, followed by coma and death. It is estimated that only about 100 people in the world have the gene that causes the condition.

Foreign Accent Syndrome is a rare speech disorder. Affected people start to speak with a different accent, usually that of another country, sometimes to the point that their native language sounds as if it were actually their second or even third language. The condition is most common after a head injury, stroke, or other damage to the central nervous system. Some versions of Foreign Accent Syndrome have a psychological trigger. There were only about 100 cases reported between 1907 and 2014.

Progeria is a rare genetic disease that causes children to age rapidly after 24 months. Some of the symptoms include slow growth, disproportionately small face, large head, short stature, and low weight. The condition is caused by mutation in the gene that makes the protein in the body responsible for shaping the nucleus within cells. Children with progeria live about 15 years and usually die from complications of heart disease. Currently, there are about 400 children around the world with the condition.

Hyperthymesia is also known as Highly Superior Autobiographical Memory (HSAM). Few people in the world have the condition, which basically means they can remember just about every day of their lives in great detail. There have been suggestions that HSAM, the cause for which is still unknown, is linked to autism and obsessive-compulsive disorder but there has been no definitive link to prove a connection.