The incidence of cystinuria in Japan.

Screening tests for cystinuria were done in approximately 110,000 children and students. The rates of discovery were chemical cystinuria 920 to 1, cystine crystalluria 16,000 to 1 and homozygous cystinuria 18,000 to 1 (8,000 to 1 if a correction was made by the rates of performances of secondary screening and urinary amino acid assay). No stone formation was observed in a 7-year followup of 6 patients considered to be homozygotes. A correlation was observed between urinary cystine and urinary uric acid levels in 39 cases of chemical cystinuria.