An established case of dentatorubral pallidoluysian atrophy (DRPLA) with unusual features on muscle biopsy.

Dentatorubral pallidoluysian atrophy (DRPLA) belongs to the group of autosomal dominant ataxias. Central nervous system pathology and inheritance are both well characterized, although the illness is rare. The presentation of a European child affected by this illness is described. He presented at 9 years of age with intractable progressive myoclonus epilepsy against a background of learning difficulties and developed progressive hypertonicity and dementia before his death at 15 years of age. Significant histological changes in a muscle biopsy were found. There was an absence of type IIB fibres and a predominance of type I fibres. Mean fibre diameter of all the fibre types was markedly reduced. All type I fibres showed an increase in lipid droplets. No previous descriptions exist of muscle histology in DRPLA. Although at least five adult family members have symptoms consistent with a diagnosis of DRPLA, their condition had not been recognized. We therefore describe the clinical picture and histological findings.