Delineation of the motor disorder of

Lesch–Nyhan disease (LND) is caused by deficiency of the purine salvage enzyme hypoxanthine-guanine phos-phoribosyltransferase (HPRT). Affected individuals exhibit over-production of uric acid, along with a charac-teristic neurobehavioural syndrome that includes mental retardation, recurrent self-injurious behaviour and motor disability. Prior studies involving relatively small numbers of patients have provided different conclusions on the nature of the motor disorder. The current study includes the results of a multi-centre international prospective study of the motor disorder in the largest cohort of patients studied to date. A total of 44 patients ranging from 2 to 38 years presented a characteristic motor syndrome that involved severe action dystoni