cystinuria /sis′tino͝or″ē·ə/ [cystine + Gk, ouron, urine] , 1. abnormal presence of the amino acid cystine in the urine collected in a 24-hour specimen. 2. an inherited defect of the renal tubules, characterized by excessive urinary excretion of cystine and several other amino acids. The disorder is caused by an autosomal-recessive trait that impairs cystine reabsorption by the kidney tubules. In high concentration, cystine tends to precipitate in the urinary tract and form kidney or bladder stones. Treatment attempts to prevent the formation of stones or to dissolve them by increasing the volume of urine flow, decreasing the pH of the urine, and increasing the solubility of cystine. In addition to a large fluid intake, sodium bicarbonate, acetazolamide, and, in refractory cases, d-penicillamine are sometimes prescribed.
