Fatal familial insomnia (FFI) is a very rare, autosomal dominant inherited, brain disease. It is caused by a mutation in a protein called prion protein (PrP): asparagine-178 is replaced by aspartic acid. The mutation changes the shape of PrP so that it becomes a prion and makes other, normal PrP molecules change to the abnormal shape. This causes amyloid plaques in the thalamus, the region of the brain responsible for regulation of sleep patterns. The dysfunction of the thalamus results in insomnia first of all, which progresses to more serious problems over several years. The age of onset is variable ranging from 18 to 60. The presentation of the disease varies considerably from person to person, even among patients from within the same family. There has only ever been one recorded case of sporadic FFI, i.e. where there was no PrP mutation and no family history. Common symptoms and signs include:
There are other "prion diseases" with different symptoms, such as Creutzfeldt-Jakob disease and also bovine spongiform encephalopathy in cows. FFI, as with other prion related diseases, is ultimately fatal and incurable. Hopes rest on the so far unsuccessful gene therapy and possibly drug development.
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