22 Hard-To-Detect Illnesses, From The Commonplace To The Truly Bizarre

12. Fatal Insomnia

One in four Americans develop insomnia each year, making it a very common disease, though usually temporary. However, while 75% of those who suffer from insomnia recover, many do not. This includes people afflicted with Fatal Insomnia, a rare form of the disorder that worsens over time and leads to death within a few months or years after it develops fully. There are two types: Fatal familial insomnia, which is passed on genetically, and sporadic fatal insomnia, which is not.