Identification of novel cystinuria mutations in pediatric patients

Cystinuria is a common inherited disorder of renal reabsorption of cystine and the dibasic amino acids. So far, mutations in two genes (SLC3A1 and SLC7A9) have been identified in cystinuria patients. Molecular searches for cystinuria mutations show that their distribution depends on the ethnic origin of the patients, but have not allowed the detection of 100% of variants. Pediatric patients representing a severe form of the disease appear to carry other mutations than those patients referred from urological centers. We analysed patients with an age of manifestation less than 15 years for mutations in the two cystinuria genes.

We screened 17 patients for mutations in SLC3A1 and SLC7A9, 15 of whom were younger than 16 years at first stone formation. The search for mutations used PCR-based standard techniques, and was focused on point mutations and larger deletions and duplications in both genes.

Apart from detection of mutations in approximately 70% of patients but identification of only 53% of alleles, we detected three novel mutations as well as three new polymorphisms.

The detection rate in young cystinuria patients is lower than that in older patients, and there is a different pattern of variants. There is evidence for other (probably genetic) factors being involved in the pathophysiology of cystinuria.