Prevalence of dentatorubral-pallidoluysian atrophy in a large series of white patients with cerebellar ataxia.

BACKGROUND Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare neurodegenerative disorder mainly diagnosed in Japan. Its prevalence is low in other countries. Three phenotypes are described: choreoathetoid movements, cerebellar ataxia, and progressive myoclonic epilepsy. OBJECTIVE To evaluate the frequency of DRPLA in European patients with sporadic or autosomal dominant cerebellar ataxia. METHODS We analyzed a series of 809 index patients with either autosomal dominant cerebellar ataxia (416 families) or progressive cerebellar ataxia without a family history of the disease (393 cases) for the DRPLA mutation. RESULTS We identified a CAG repeat expansion in the DRPLA gene in one family and in one patient without a family history. The familial case illustrates the phenomenon of anticipation and the previously established correlation between the phenotype and size of the expansion. A censored-history family or expansion of large normal CAG repeats during paternal transmission could be implicated in the patient without a family history. CONCLUSIONS This study enables us to estimate the frequency of the disease as 0.25% in both families with autosomal dominant cerebellar ataxia and sporadic cases of ataxia in our series, confirming the very low frequency of DRPLA in Europe. In both familial and sporadic cases, molecular testing for DRPLA could be restricted to patients with ataxia with one of the following features: chorea, dementia, or myoclonic epilepsy.