Fatal familial insomnia (FFI) typically shows first signs in middle age and is genetic. It arises as a result of a mutation of the PRNP gene. The most crucial symptom is difficulty falling asleep and maintaining sleep. Nerve damage and loss are observed in the thalamus, a center with essential sleep-related functions in the brain. As a result, complaints progress more and more. Unfortunately, there is no cure. The disease is fatal.