Type I cystinuria and its genetic basis in a population of Turkish school children
Objectives: Cystinuria is a common inherited disorder characterized by an abnormal urinary excretion of cystine and dibasic amino acids resulting in nephrolithiasis. The SLC3A1 gene, which encodes a dibasic amino acid transporter protein, is involved in the pathogenesis of cystinuria. In the present study we aimed to investigate the prevalence of cystinuria among children in Sivas province (Central Anatolia, Turkey) and to study M467T and M467K mutations and 231T/A polymorphism in patients with cystinuria. Methods: A total of 8500 children were screened for cystinuria. The cyanide-nitroprusside test was applied to urine samples of all children. Children having a positive cyanide-nitroprusside test were further analyzed. M467T and M467K mutations (exon 8) and 231T/A polymorphism (exon 1) in the SCL3A1 gene were studied using a restriction fragment length polymorphism (RFLP) assay. Results: We have found that the prevalence of cystinuria (11 cystinuric patients) is 1/772 in our population. Results of mutation analysis in the patients with cystinuria showed that M467T was the only mutation that was found in six cystinuric patients. One patient was homozygous and five were heterozygous for this mutation. Conclusions: The frequency of cystinuria in Sivas Province is the highest among the other populations studied to date. The frequency of M467T mutation is relatively higher than those reported for most populations. High frequency of cystinuria in this region could be due to consanguineous marriages.