PRION DISEASE (PRP-A117V) PRESENTING WITH ATAXIA INSTEAD OF DEMENTIA

Gerstmann-Straussler-Scheinker disease (GSS) is caused by several diff erent point mutations of the prion protein (PrP) gene, each of which g enerally produces a distinct clinical phenotype. An ataxic form of GSS is genetically linked to a mutation at codon 102 (CCG-->CTG) leading to the substitution of leucine for proline, while a ''telencephalic'' variant of GSS, in which dementia is the predominant symptom and ataxi a is minimal, has been described in two kindreds with a mutation at co don 117 (GCA-->GTG) resulting in the substitution of valine for alanin e. In this report, we present a family with ataxic GSS that has, howev er, the same mutation at codon 117 as is present in the telencephalic variant of GSS. Other than an additional silent mutation (GCA-->GCG) a t codon 117 on the normal allele, there were no other mutations detect ed. At the polymorphic codon 129, valine was encoded by both alleles i n the proband that we studied. Why this family with prion disease (PrP -A117V) should present with ataxia instead of dementia,which was found in two previously identified families with the same PrP gene mutation , remains to be establish.