Cystinuria is an autosomal recessive disorder caused by mutations in either the SLC3A1 or the SLC7A9 genes, resulting in a disordered amino acid transport in the proximal tubule,28 Cystinuria is characterized by urinary hyperexcretion of cystine and the dibasic amino acids lysine, ornithine, and arginine. This evidence concerns the gene SLC7A9 and cystinuria.