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A subtype of sporadic prion disease mimicking fatal familial insomnia

P Parchi1, S Capellari, S Chin

  • 1Division of Neuropathology, Institute of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.

Neurology
|June 17, 1999
PubMed
Abstract

Insights

A new variant of sporadic prion disease, termed "sporadic fatal insomnia," closely resembles fatal familial insomnia (FFI) but lacks the characteristic PRNP mutation and specific prion protein features.

Area of Science:

  • Neuroscience
  • Prion Diseases
  • Genetics

Background:

  • Fatal familial insomnia (FFI) is a rare prion disease causing severe sleep disturbances, autonomic dysfunction, and motor deficits.
  • Pathologically, FFI involves atrophy of thalamic nuclei and the inferior olive.
  • FFI is associated with the D178N mutation in the prion protein gene (PRNP) and specific abnormal prion protein (PrP(Sc)) characteristics.

Observation:

  • Five subjects presented with clinical and histopathological features nearly identical to FFI.
  • These subjects exhibited PrP(Sc) type 2, similar in amount and distribution to FFI.
  • However, the PrP(Sc) in these subjects lacked the underrepresentation of the unglycosylated form seen in FFI.

Findings:

  • None of the subjects carried the D178N PRNP mutation.
  • All subjects were homozygous for methionine at codon 129 of the PRNP gene.
  • The observed prion protein characteristics differed from those typically found in FFI.

Implications:

  • This study identifies a distinct prion disease variant.
  • The findings suggest a sporadic form of fatal insomnia.
  • The proposed term "sporadic fatal insomnia" aids in classifying this condition.

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