HPRT1 and Lesch-Nyhan syndrome: Lesch-Nyhan disease (LND) is caused by pathogenic variants in the HPRT1 gene encoding the purine salvage enzyme hypoxanthine-guanine phosphoribosyl transferase (HGprt).1,2 Absence of HGprt causes hyperuricemia and a neurobehavioral phenotype characterized by dystonia, cognitive deficits, and behavioral abnormalities including self-injury.2,3 Usually, the movement disorder prevents ambulation, and patients require assistance with all activities of daily living.3 Irresistible self-injury is the most troublesome aspect of LND.