Homozygous cystinuria in New South Wales. A study of 110 individuals with cystinuria ascertained by methods other than neonatal screening.

Homozygous cystinuria was ascertained in 110 individuals (44 men) from 78 families because of symptoms in the propositi. The most common renal symptoms were calculi which occurred in 91% of the propositi and in 52% of affected family members. One-third of patients had urinary tract infections. There was a high rate of renal morbidity at an early age; 16 patients had undergone nephrectomy at a mean age of 25 years (range, 12-40 years). Two-thirds of subjects had type I cystinuria on family testing--the same ratio as that reported in a previous study of cases detected by newborn screening in the same population--which eliminates genetic type as a risk factor for stone formation. On the basis of all data, a 62% probability of stone formation by the age of 25 years in patients with cystinuria was estimated. The patients were shorter than Australian controls, and an association between gout and cystinuria was found in adult men.