A Case of Cystinuria with Multiple Renal Stones in an 8-month-old Girl

ABSTRACT

Cystinuria is an autosomal recessive disease characterized by impaired transport of cystine and dibasic amino acids in the proximal renal tubule, resulting in the formation of cystine stones. It is believed to account for about 1% of all kidney stones and up to 10% of pediatric stones. Here we report a case of cystinuria with multiple renal stones confirmed by genetic mutational analysis. An 8-month-old girl was admitted to AMC with persistent fever and multiple renal stones. A renal sonogram showed multiple stones at the right renal pelvis, right distal ureter, and left renal medullary portion. An approximately 1 cm renal stone was extracted spontaneously, and stone analysis revealed it to be composed entirely of cystine. Cystinuria was confirmed by increased urine dibasic amino acid levels, including cysteine, and genetic mutational analysis showed the patient to be a homozygote for the pathogenic c. 1820del (p.L607fs) of SLC3A1. Despite treatment with oral hydration and urinary alkalinization, and restricted intake of animal protein, the stones increased in size and number. The patient has since been treated with tiopronin.