[Gerstmann-Sträussler-Scheinker disease with heterozygous codon change at prion protein codon 129]

A 53-year-old male was admitted to our hospital for progressive dementia and gait disturbance which had started at the age of 48. Examination indicated dementia, dysarthria, dysphagia, bilateral pyramidal signs, apraxia of the limbs, and extrapyramidal signs such as fine finger tremors, and rigidity of limbs. There were no cerebellar signs or myoclonus. His mother and elder brother showed similar symptoms and died at the ages of 53 and 50, respectively. EEG was normal. CT and MRI showed mild brain atrophy, but no cerebellar atrophy. T2 weighted image indicated low intensity areas covering bilateral caudate nuclei and putamina. A heterozygous amino acid change from methionine to valine was noted at codon 129 of the prion protein of the patient as well as in one of his son. The most likely diagnosis was Gerstmann-Sträussler-Scheinker (GSS) disease without cerebellar atrophy. GSS may include a broad spectrum of brain pathology. Whether the codon change is associated with pathology without cerebellar atrophy is a problem that awaits further investigation.