What is the pathophysiology of fatal familial insomnia (FFI)?

Updated: Sep 11, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

A rare condition, fatal familial insomnia (FFI, previously known as thalamic dementia) is an autosomal dominant human prion disease caused by changes in the PRNP (prion protein) gene. FFI involves a severe disruption of the physiologic sleep pattern that progresses to hallucinations, a rise in catecholamine levels, autonomic disturbances (tachycardia, hypertension, hyperthermia, and diaphoresis), and significant cognitive and motor deficits. Mean age of onset is 50 years, and average survival is 18 months. [36, 37, 38]

FFI and a subtype of familial Creutzfeldt-Jakob disease (CJD) share the same mutation at codon 178 (Asn178) in the PRNP gene. They differ in that a methionine-valine polymorphism is present at codon 129 in PRNP in this subtype of familial CJD. [39]

Sporadic fatal insomnia (SFI) shares a similar clinic course with FFI but does not appear to be inherited. A mutation at codon 178 of the PRNP gene is not found in these patients, but patients have been found to be homozygous for methionine at codon 129 in PRNP. [40]


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