cystinuria

Cystinuria is an inherited autosomal recessive disease characterized by high concentrations of the amino acid cystine in the urine, leading to the formation of cystine stones in the kidneys, ureters, and bladder. It is a type of aminoaciduria. "Cystine", not "cysteine," is implicated in this disease; the former is a dimer of the latter.

==Presentation== Cystinuria is a cause of recurrent kidney stones. It is a disease involving the defective transepithelial transport of cystine and dibasic amino acids in the kidney and intestine and is one of many causes of kidney stones. If not treated properly, the disease could cause serious damage to the kidneys and surrounding organs, and in some rare cases death. The stones may be identified by a positive nitroprusside cyanide test. The crystals are usually hexagonal, translucent, and white. Upon removal, the stones may be pink or yellow, but later they turn greenish due to exposure to air. Cystinuria is usually asymptomatic when no stone is formed. However, once a stone is formed, signs and symptoms can occur: Nausea Flank pain Hematuria Urinary tract infections Rarely, acute or chronic kidney disease