Which of the following diseases is characterized by familial fatal insomnia?

• A. Gerstmann-Straüssler-Scheinker disease
• B. Creutzfeldt-Jakob disease
• C. Mad cow disease
• D. Familial fatal insomnia

Answer: (D)

Familial fatal insomnia is a rare genetic disorder specifically characterized by an inability to sleep, leading to severe physical and mental deterioration. This condition is caused by mutations in the PRNP gene, which encodes the prion protein. As individuals with familial fatal insomnia progress through the disease, they experience not only insomnia but also cognitive decline, autonomic dysfunction, and eventually death, often within a few months to a few years after symptoms begin.

While the other diseases listed can involve prion proteins and other neurological symptoms, they do not specifically encompass the hallmark feature of familial fatal insomnia. The distinct nature of the symptoms and the specific genetic background that defines familial fatal insomnia makes it clear that it is the correct choice in this context. Thus, the answer reflects the uniqueness of the disease’s traits as compared to other prion diseases.