820 Cystinuria Over Two Generations

Abstract

Cystinuria is an autosomal recessive disorder that is characterized by an impaired tubular transport of cystine and dibasic aminoacids, resulting in cystine urolithiasis. The transport of these amino acids is mediated by the rBAT/b0,+ AT transporter, the subunits of which are encoded by the genes SLC3A1, located on chromosome 2p16.3-21, and SLC7A9, located on chromosome 19q12-13.1. In this work we present a family in which cystinuria was manifested in two generation. The index case is a female, aged 9 years when she was diagnosed with a kidney stone and underwent surgery. Nitroprusside test was positive and urinary excretion of cystine was high (127.5 mM/M creatinine, normal 0.6-20.0 mM/M creatinine). The family screening revealed that two siblings (sister and brother) had positive nitroprusside test and increased urinary excretion of cystine. The mother had history of surgery for nephrolithiasis, had positive nitroprusside test and increased urinary excretion of cystine. The mutational analysis of the SLC3A1 gene revealed that the index case and the mother were compound heterozygote (T216M/M467T), while the female and the male siblings were homozygote for M467T mutation. The father was heterozygote for M467T mutation. The ethnic origin of the patients is Egyptian. To the best of our knowledge this is the first report of cystinuria occurring over two generations.