Cystine Crystals

Cystine crystals are not found in the urine of normal individuals. The presence of cystine crystals almost always indicates “cystinuria,” a disease affecting the metabolism of three of the 20 amino acids that make up proteins. A reabsorption problem of these three amino acids (arginine, lysine and ornithine) causes the overproduction of cystine, a very insoluble product that tends to form crystals in the urine and, more importantly, causes the repeated formation of cystine stones.