children s health issues
Cystinuria
Introduction
Cystinuria is a rare hereditary kidney disorder that results in excretion of the amino acid cystine into the urine, often causing cystine stones to form in the urinary tract. (See also Introduction to Congenital Kidney Tubular Disorders and Cystinuria is caused by an inherited defect of the kidney tubules. The defect causes people to excrete excessive amounts of the amino acid cystine into the urine (amino acids are the building blocks of proteins). The excess cystine causes Stones in the Urinary Tract to form in the kidneys, bladder, renal pelvis (the area where urine collects and flows out of the kidney), or ureters (the long, narrow tubes that carry urine from the kidneys to the bladder). There are two gene abnormalities that cause most cystinuria. The genes are Recessive disorders , so people with the disorder must have inherited two abnormal genes, one from each parent ( see Figure: Sometimes, a person who has only one abnormal gene (a carrier), such as a parent of a person who has cystinuria, may excrete larger than normal amounts of cystine into the urine but seldom enough to form cystine stones. Boys are generally affected more than girls. 