In our “Ask a kidney stone doctor” section, we field questions from stone formers or their family members. Today’s question is about cystinuria. See other questions and answers or ask your own question here.
October 11, 2011
Question from the UK:
“How common is it for a patient with homozygous cystinurea to never form a stone?”
Cystinuria is a rare cause of kidney stones overall, accounting for 1-2% or less of all stones. In children however, it accounts for up to 6-8% of stones. It is caused by a defect in the transport of amino acids across the cellular membrane of the renal proximal tubule and small intestine. Cystinuria is an inherited disorder.
Because of the relative rarity of cystinuria, there is limited reliable, long term data on the risk of stones. A review of the literature found the following:
Most but not all patients with homozygous cystinuria (carrying two copies of the abnormal gene) appear to develop stones throughout their lifetime. A study by the International Cystinuria Consortium reported that only 6% of individuals with homozygous cystinuria did not produce stones. The age at which individuals first formed stones also varied, with many experiencing stones between 11 and 20 years of age but with some forming stones before the age of 3.
Complicating matters, cystinuria is classified into types A, B, and AB, depending on the specific combination of two known inheritable genes (SLC3A1 and SLC7A9) that can cause the disease. The risk and age of onset of developing stones varies with which type an individual has.
Pathophysiology and Treatment of Cystinuria. Chillaron et al. Nature Reviews Nephrology. 2010.
Cystinuria Subtype and the Risk of Nephrolithiasis. Goodyer et al. Kidney International. 1998.
Before making any medical decisions, always consult with your treating physician.