Inherited prion diseases

Gerstmann-Straussler-Scheinker disease

The first case was described by Gerstmann in 1928 and was followed by a more detailed report on seven other affected members of the same family in 1936. (56) The classical presentation of GSS is with a chronic cerebellar ataxia accompanied by pyramidal features, with dementia occurring later in a much more prolonged clinical course than that seen in CJD. The mean duration is around 5 years, with onset usually in either the third or fourth decades. Histologically, the hallmark is the presence of multicentric amyloid plaques. Spongiform change, neuronal loss, astrocytosis, and white-matter loss are also usually present. Numerous GSS kindreds from several countries (including the original Austrian family described by Gerstmann, Straussler, and Scheinker in 1936) have now been demonstrated to have mutations in the PrP gene. GSS is an autosomal dominant disorder which can now be classified within the spectrum of inherited prion disease.

Classification and clinical features of inherited prion diseases

The identification of one of the pathogenic PrP gene mutations in a case with neurodegenerative disease allows not only molecular diagnosis of an inherited prion disease but also its subclassification according to mutation. Pathogenic mutations reported to date in the human PrP gene consist of two groups:

1. point mutations within the coding sequence resulting in amino acid substitutions in PrP or in one case production of a stop codon resulting in expression of a truncated PrP;

2. insertions encoding additional integral copies of an octapeptide repeat present in a tandem array of five copies in the normal protein.

A suggested notation for these diseases is 'inherited prion disease (PrP mutation)', for instance: inherited prion disease (PrP 144-bp insertion) or inherited prion disease (PrP P102L).

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