Cystinuria

Alternative names:

cystine stones; stones - cystine

Definition:

A disorder characterized by stones in the kidney, ureter, and bladder; caused by excessive excretion of certain amino acids (protein building blocks) because of genetic abnormality. (See also nephrolithiasis).

Causes, incidence, and risk factors:

Cystinuria is an inherited autosomal recessive disorder. The kidneys do not adequately resorb certain amino acids during the filtering process, resulting in excess excretion of these amino acids. The amino acids may precipitate and form crystals or stones in the kidneys, ureters, or bladder.

The disorder is usually diagnosed after an episode of stones, where analysis of the composition of the stones indicates cystine. Less than 3% of known urinary tract stones are cystine stones.

Cystinuria affects approximately 1 out of 10,000 people. Cystine stones are most common in young adults under age 40.