A new French-Canadian family affected by hyperargininaemia.

A new French-Canadian family from the province of Quebec is reported, in which a male child was diagnosed as hyperargininaemic after showing positive tests for cystinuria on neonatal screening. The child has no residual activity of erythrocyte arginase, and a plasma arginine level of 633 mumol/l. Both parents have 32-38% of arginase activity. A newborn sister has normal enzyme levels. The propositus did not show abnormal plasma ammonia elevation even after a protein tolerance test (1.5 g protein/kg body weight) but excretes high levels of urinary orotate (845 mg/g creatinine). At 3 1/2 years of age the hyperargininaemic child had started showing abnormal gait, ataxia and slowing of intellectual development. It is suggested that all newborn children showing cystinuria-lysinuria pattern of amino acid excretion be tested for arginase deficiency.