Cystinuria: cause of recurrent renal stones in a 4-year-old girl.

This paper presents the case report of a 4-year and 6-month old girl with cystinuria. She clinically presented with recurrent radiopaque renal stones since the age of 3 years. She received 2 subsequent operations of pyelolithotomy combined with ureterolithotomy at the age of 3 years 6 months, and pyelolithotomy alone at the age of 5 years. She was initially diagnosed as having cystinuria by the presence of hexagonal plate crystals in her acidified urine and positive for the urinary cyanide-nitroprusside test. The diagnosis was confirmed by urinary amino acid analysis using quantitative ion-exchange chromatography which revealed increased amounts of cystine and dibasic amino acids of lysine and ornithine. In spite of maintaining a high fluid intake and alkalinizing urine by giving potassium citrate after the first operation, recurrent renal stones were found. Therefore, after the second operation, D-penicillamine was additionally introduced. During the 18-month follow-up, although there were recurrent renal stones, the rate of stone formation was slower. To the authors' knowledge, this is the first case report in Thailand.