Fatal familial insomnia
| Fatal familial insomnia | |
|---|---|
 |
|
| Autosomal dominant pattern | |
| Classification and external resources | |
| Specialty | Sleep medicine |
| ICD-10 | A81.9 |
| ICD-9-CM | 046.72 |
| OMIM | 600072 |
| DiseasesDB | 32177 |
| MeSH | D034062 |
Fatal familial insomnia (FFI) is an extremely rare autosomal dominant inherited prion disease of the brain. It is almost always caused by a mutation to the protein PrPC, but can also develop spontaneously in patients with a non-inherited mutation variant called sporadic fatal insomnia (sFI). FFI has no known cure and involves progressively worsening insomnia, which leads to hallucinations, delirium, confusional states like that of dementia, and eventually, death. The average survival time for patients diagnosed with FFI after the onset of symptoms is 18 months.
The mutated protein, called PrPSc, has been found in just 40 families worldwide, affecting about 100 people; if only one parent has the gene, the offspring have a 50% risk of inheriting it and developing the disease. With onset usually around middle age, it is essential that a potential patient be tested if they wish to avoid passing FFI on to their children. The first recorded case was an Italian man, who died in Venice in 1765.
The age of onset is variable, ranging from 18 to 60, with an average of 50. The disease can be detected prior to onset by genetic testing. Death usually occurs between seven and 36 months from onset. The presentation of the disease varies considerably from person to person, even among patients from within the same family.
The disease has four stages:
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. Constipation is common as well. As the disease progresses, the patient is forever stuck in a state of pre-sleep limbo, or hypnagogia, which is the state just before sleep in healthy individuals. During these stages, it is common for patients to repeatedly move their limbs as if dreaming.
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