Cystinuria is a genetic disease where cystine, a xxx, isn't properly absorbed in the kidneys, resulting in too much cystine in the urine. The excess cystine can also form crystals or stones in the kidney or bladder, and cystinuria is a cause of persistent kidney stones.
Treatment can involve drinking lots of water, nutritional supplements, and dietary changes. If this isn't effective, medications like penicillamine (Depen, Cuprimine) or tiopronin (Thiola) can also help prevent kidney stones.