Question: What is FFI, fatal familial insomnia

Context:
Fatal familial insomnia is a rare disease caused by a D178N mutation in combination with methionine (Met) at codon 129 in the mutated allele of PRNP (D178N-129M haplotype).
FFI is manifested by sleep disturbances with insomnia, autonomic disorders and spontaneous and evoked myoclonus, among other symptoms
Familial fatal insomnia (FFI) is fatal disorder characterized by damage to select thalamic nuclei, together with progressive insomnia and dysautonomia.
Point mutations or the insertions of one or more copies of a 24 bp repeat are associated with familial human prion diseases including familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. 
Fatal familial insomnia (FFI) is a unique hereditary prion disease with characteristic disturbances of sleep.
Fatal familial insomnia (FFI) is a rare hereditary human prion disease with unique clinical features including progressive sleep impairment and autonomic dysfunction.
Fatal familial insomnia (FFI), a condition characterized by inability to sleep, dysautonomia, motor disturbances, and selective thalamic atrophy is a prion disease linked to a GAC----AAC mutation at codon 178 of the prion gene.
Fatal familial insomnia (FFI), or familial selective thalamic degeneration with a mutation at codon 178 of the prion protein (PrP) gene, is a rapidly progressive autosomal dominant disease characterized by progressive insomnia, dysautonomia, and myoclonus.
BACKGROUND: Fatal familial insomnia (FFI) is an autosomal dominant disease linked to a mutation in the prion protein gene. Fatal familial insomnia is characterized by sleep disturbance and loss of neurons, with gliosis in the thalamic nuclei.OBJECTIVE: To describe the clinical, neurophysiological, radiological, and neuropathological data in a Chinese family with FFI.SETTING: Tertiary referral university hospital setting.PATIENTS: Patient 1 was a 36-year-old man who presented with insomnia and myoclonus.
Fatal familial insomnia (FFI) is a rare genetic disease characterized by intractable insomnia, dysautonomia, and dementia.
FFI is characterized clinically by untreatable progressive insomnia, dysautonomia, and motor dysfunctions and is characterized pathologically by selective thalamic atrophy. 
FFI is associated with an aspartic acid to asparagine mutation at codon 178 of the PrP gene (D178N) in conjunction with methionine at the codon 129 polymorphic site on the mutant allele (cis-129M).
The propositus had behavioral, sleep, cognitive, and motor impairment associated with thalamic and olivary atrophy
 Sporadic fatal insomnia (sFI) and fatal familial insomnia (FFI) are rare human prion diseases.
Fatal familial insomnia (FFI) is an autosomal dominant prion disease characterized clinically by inattention, sleep loss, dysautonomia, and motor signs. 

Answer: Familial fatal insomnia (FFI) is a prion disease caused by a mutation (D178N-129M haplotype) in the Prion Protein gene (PRNP). FFI is manifested by sleep disturbances with insomnia, autonomic disorders and spontaneous and evoked myoclonus, among other symptoms. FFI is considered to be a rare disease.