Reviewed March 2006
What is cystinuria?
Cystinuria is a condition characterized by the buildup of cystine crystals or stones in the kidneys and bladder. Cystine is an amino acid, one of the building blocks of proteins. Normally, cystine is reabsorbed back into the bloodstream after blood entering the kidneys is filtered to create urine. Only small amounts of cystine can stay dissolved in urine. People with cystinuria cannot properly reabsorb cystine into their bloodstream. As urine becomes more concentrated in the kidneys, the cystine cannot stay dissolved and forms crystals. As these crystals become larger, they form stones that may lodge in the kidneys or in the bladder. Sometimes cystine crystals combine with calcium in the kidneys to form large stones. Blockages in the urinary tract by these crystals and stones reduce the ability of the kidneys to eliminate wastes through urine. The stones also provide sites where bacteria may cause infections.
How common is cystinuria?
Cystinuria affects approximately 1 in 10,000 people.
What genes are related to cystinuria?
Mutations in the SLC3A1 and SLC7A9 genes cause cystinuria.
The SLC3A1 and SLC7A9 genes provide instructions for producing the two parts of a transporter protein that is made primarily in the kidneys. Normally this protein allows certain amino acids, including cystine, to be reabsorbed into the blood from the filtered fluid that will become urine. Mutations in either of these genes disrupt the ability of this transporter protein to reabsorb these amino acids, allowing them to become concentrated in the urine. As the levels of cystine in the urine increase, the crystals typical of cystinuria are able to form. The other amino acids that are not reabsorbed do not create crystals in urine.
Read more about the SLC3A1 and SLC7A9 genes.
How do people inherit cystinuria?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about treatment for cystinuria?
These resources address the management of cystinuria and may include treatment providers.
You might also find information on treatment of cystinuria in
Educational resources and Patient support.
Where can I find additional information about cystinuria?
What other names do people use for cystinuria?
What if I still have specific questions about cystinuria?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding cystinuria?
The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
healthcare professional.
See How can I find a genetics professional in my area? in the Handbook.