Fatal familial insomnia (FFI) is a rare type of human transmissible spongiform encephalopathy (TSE), characterized by refractory insomnia with dreams and hallucinations, vegetative disorders (abolition of circadian rythm, sympathic hyperactivity, sphincter disorders), motor impairment and dementia that may occur late in the disease course. FFI was first described in Italy. Several families have been reported in France. Average age of onset is 51. Myoclonus is rare. The EEG is abnormal but not periodic when the subject is awake, while it is marked by the progressive disappearance of delta activity, spindles, and «K complexes» when the subject is sleeping. There are abnormal stages of paradoxal sleep. Neuropathological findings (neuronal loss, gliosis) are particular: they are mainly located in the dorsomedian and anterior nuclei of the thalamus. Spongiosis is mild. There are no amyloid plaques. The disease is due to a defective gene encoding the prion protein (PRNP gene). The genetic defect is a point mutation in codon 178 coupled on the same allele with the methionine codon at position 129. If codon 129 encodes a valine, the clinical and neuropathological signs are those of the genetic form of Creutzfeld-Jakob's disease (CJD). FFI has been successfully transmitted to mice by 2 different research teams, which proves that it belongs to TSE. To date, there is no treatment of the underlying pathological mechanisms of the disease. The condition is fatal within 6 to 32 months.
Last update: August 2004