Fatal insomnia is a rare disorder that results in trouble sleeping. The problems sleeping typically start out gradually and worsen over time. Other symptoms may include speech problems, coordination problems, and dementia. It results in death within a few months to a few years.

It is a prion disease of the brain. It is usually caused by a mutation to the protein PrPC. It has two forms: fatal familial insomnia (FFI), which is autosomal dominant and sporadic fatal insomnia (sFI) which is due to a noninherited mutation. Diagnosis is based on a sleep study, PET scan, and genetic testing.

The disease has four stages:

1. The person has increasing insomnia, resulting in panic attacks, paranoia, and phobias. This stage lasts for about 4 months.

2. Hallucinations and panic attacks become noticeable, continuing for about 5 months.

3. Complete inability to sleep is followed by rapid loss of weight. This lasts for about 3 months.

4. Dementia, during which the person becomes unresponsive or mute over the course of 6 months, is the final stage of the disease, after which death follows.

Other symptoms include profuse sweating, pinpoint pupils, the sudden entrance into menopause for women and impotence for men, neck stiffness, and elevation of blood pressure and heart rate.

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