Cystinuria is a rare genetic disorder that causes a buildup of an amino acid called cystine in the urine. This can result in the formation of cystine kidney stones.
Cystine stones are often larger, harder and form more frequently than other kinds of kidney stones. Due to the larger stone size, cystine stones may be more difficult to pass, often requiring surgical procedures to remove.
Stones can create blockages in the urinary tract and reduce the ability of the kidneys to eliminate waste through urine. The stones also provide sites where bacteria may cause infections.
Signs and symptoms of the condition are related to the presence of stones and may include blood in the urine, flank pain, and frequent urinary tract infections.
Cystinuria is inherited in an autosomal recessive genetic manner, meaning that a child is affected when each parent passes on one copy of the mutated gene. Symptoms tend to emerge when patients are between 10 and 30 years old. More than 80 percent of people with cystinuria develop their first stone by the age of 20. More than 25 percent will develop cystine stones by the age of 10. The disorder occurs in approximately 1 in 10,000 people in the United States.
Resources: PreventCystineStones.com; NIH Genetics Home Reference, National Organization for Rare Disorders.