PRPS1 and nervous system disorder: Our finding of a subject with adolescent-onset ataxia with neuropathy, optic atrophy, hearing loss, and mild atrophy of the cerebellum without evidence of neurological disease in the parental generation places PRPS1-disease in the differential diagnosis of many adult-onset autosomal-recessive and mitochondrial ataxias where such findings are common and which might be mimicked by PRPS1-disease.