Cystinuria is a genetic disorder that affects the kidneys, leading to the formation of cystine stones. It occurs when the body fails to properly reabsorb the amino acid cystine, causing it to accumulate in the urine. This can result in painful kidney stones, urinary tract infections, and other complications. The condition is inherited in an autosomal recessive pattern, meaning both parents must carry the gene for a child to be affected. Diagnosis typically involves urine tests to measure amino acid levels, and treatment may include increased fluid intake, medications, and, in some cases, surgery to remove stones.