rare x-linked disorder of purine metabolism, due to deficiency of hypoxanthine phosphoribosyltransferase; affected individuals are normal in the first year of life and then develop psychomotor retardation, extrapyramidal movement disorders, progressive spasticity, and seizures; self-destructive behaviors such as biting of fingers and lips are seen frequently; intellectual impairment may also occur but is typically not severe; elevation of uric acid in the serum leads to the development of renal calculi and gouty arthritis.