Investigation of recessive ataxia loci in patients with young age of onset.

Autosomal recessive cerebellar ataxias are a phenotypically and genetically heterogeneous group of diseases. Major forms can be distinguished on the basis of clinical signs, age of onset, biochemical parameters or genotypes. To develop rational diagnostic strategies, phenotypic information, e.g., age of onset combined with population-specific disease frequencies could be highly favourable. We tested this hypothesis for single candidate loci and mutations in North European ataxia patients with juvenile and early adult onset. While we could prove that Friedreich ataxia (FRDA) is frequent in Germany, only few patients with ataxia-oculomotor apraxia type 1 (AOA1) and type 2 (AOA2) were diagnosed. The frequency of the mitochondrial recessive ataxia syndrome (MIRAS) and the infantile onset spinocerebellar ataxia (IOSCA) in this population remains unknown since no case with the common mutation of the corresponding gene was detected.