LETTERS TO THE EDITOR Familial Creutzfeldt-Jakob disease with

presenting as cerebellar ataxia without insomnia Fatal familial insomnia (FFI) is a prion disease clinically characterised by progressive insomnia and dysautonomia, and associated with an aspartic acid to asparagine mutation at the codon 178 (D178N) of the prion pro-tein gene (PRNP).1 This mutation is also associated with familial Creutzfeldt-Jakob disease (CJD). These phenotypes have been held to depend on the polymorphism at the codon 129. FFI and CJD phenotypes are associated with methionine (129M) and valine (129V) polymorphisms, respectively.2 However, the diverse phenotypes can b