Type I cystinuria and its genetic basis in a population of Turkish school children

Report of SLC3A1/rBAT gene mutations in Iranian cystinuria patients: A direct sequencing study

Background:

Considering a few studies on the genetic basis of the cystinuria in the Middle East and the population-specific distribution of mutations in the SLC3A1, we tried to find genetic variants in three exons (1, 3, and 8) of SLC3A1.

Materials and Methods:

In this study, exons 1, 3, and 8 of SLC3A1 gene of 25 unrelated cystinuria patients searched for genetic variations by polymerase chain reaction and sequencing.

Results:

There were five different variations in our studied population. We found one mutation in the SLC3A1 gene including missense variant M467K and identified three polymorphisms: nonsynonymous variant G38G, c. 610 + 169C>T and c. 610 + 147C>G within the SLC3A1 gene, and one new variant.

Conclusion:

Our results confirm that cystinuria is a heterogeneous disorder at the molecular level and more studies are needed to identify the distribution and frequency of mutations causing cystinuria in the Iranian population.

Mutation analysis of SLC3A1 and SLC7A9 genes in patients with cystinuria

Cystinuria is an autosomal inherited disorder of renal reabsorption of cystine, arginine, lysine, and ornithine. Increased urinary excretion of cystine results in the formation of kidney stones. Considering the few studies on the genetic basis of the cystinuria in the Middle East and the population-specific distribution of mutations in the SLC3A1 and SLC7A9 genes, in the present study, mutation analysis of these two genes was performed in a cohort of Iranian patients with cystinuria. Thirty unrelated cystinuria patients were analyzed for four of the most common mutations using ARMS-PCR (M467T, T216M) and RFLP-PCR (G105R, R333W) methods. For negative sample, two exons of both genes, which harbor many mutations, were subject to DNA sequencing. Eight variants were identified including missense, polymorphism, intron variant, and a novel variant. The most frequent mutations were not detected in our patients and only G105R was found. Since the molecular genetic testing results may influence the therapy and prognosis of cystinuria, this paper contributes to understanding of the molecular basis of cystinuria in the Iranian patients.

Multimodal treatments of cystine stones: an observational, retrospective single-center analysis of 14 cases

Purpose

To document the experiences of a single institution in evaluating the clinical courses and treatment outcomes of patients with cystine stones.

Materials and Methods

The clinical data of 14 patients with cystine stones who were treated at our institution from March 1994 to July 2012 were reviewed. These data included age at first visit, gender, family history, body mass index, presence of a single kidney, stone locations, stone burden, routine urinalysis, and culture. In addition, we also analyzed data on surgery, shock wave lithotripsy, medical treatment, stone recurrence or regrowth, and overall treatment success rates.

Results

The mean age of our patients at their first visit was 19.6±5.0 years, and eight patients were males. The median stone burden and mean urine pH before each surgery were 6.5 cm² and 6.5±0.9, respectively. Two patients had a family history of cystine stones. Patients underwent surgery an average of 2.7 times. The median interval between surgeries was 27.3 months, and 1 open surgery, 12 percutaneous nephrolithotomies, and 25 ureterorenoscopies were performed. Potassium citrate or sodium bicarbonate was used in nine cases. D-Penicillamine was continuously used in three patients. Patients had an average incidence of 3.2 recurrences or regrowth of stones during the median follow-up period of 60.5 months.

Conclusions

Patients with cystine stones have high recurrence or regrowth rates and relatively large stone burdens. Adequate treatment schedules must therefore be established in these cases to prevent possible deterioration of renal function.

Clinical characteristics and metabolic abnormalities in preschool-age children with urolithiasis in southeast Anatolia

OBJECTIVE

Data on urolithiasis in preschool-age children are limited. The aim of this study was to investigate the metabolic etiology and clinical findings of preschool-age children with urolithiasis.

METHODS

The medical records of 143 preschool-age children (81 boys, 62 girls, aged 2-6 years) with urolithiasis were retrospectively analyzed. Results of physical examination, serum biochemistry, and urine metabolic evaluation (including urinary citrate, oxalate, calcium, uric acid, cystine, and magnesium) were recorded.

RESULTS

The mean age at diagnosis was 3.7 ± 1.3 years. A family history of stone disease was found in 79.7% of patients, and 37% of parents had consanguineous marriages. The most common presenting symptoms were hematuria (33%) and urinary tract infection (UTI; 29%). Metabolic abnormalities were found in 119 (83.2%) patients, including hyperuricosuria in 24.5%, hypocitraturia in 23.8%, hyperoxaluria in 21.7%, hypercalciuria in 21.0%, cystinuria in 7.7%, and hypomagnesuria in 1.4%. Multiple metabolic abnormalities were found in 24 (16.8%) patients. Results of 28 stone analyses revealed calcium oxalate or phosphate, cystine, and uric acid in 15, nine, and four of the patients, respectively. (99m)Technetium-dimercaptosuccinic acid renal scintigraphy revealed that 27.8% of the children with UTI had renal parenchymal scarring, with only four of them having vesicoureteral reflux.

CONCLUSION

The most frequent metabolic abnormalities in preschool-age children with urolithiasis were hyperuricosuria and hypocitraturia. A comprehensive investigation of stone disease in children presenting with hematuria and UTI is important to prevent the development of renal parenchymal scarring.

Molecular characterization of cystinuria in south-eastern European countries

Cystinuria is an autosomal recessive disorder caused by defective transport of cystine and dibasic amino acids in the proximal renal tubules and small intestine. So far, more than 128 mutations in SLC3A1 gene, and 93 in SLC7A9 gene have been described as a cause of cystinuria. We present a molecular characterization of the cystinuria in 47 unrelated south-east European families. The molecular methodology included direct sequencing, single strand conformational polymorphism, and restriction fragment length polymorphism. A total of 93 (94.9 %) out of 98 unrelated cystinuric chromosomes have been characterized. Mutations in SLC3A1 gene account for 64.3 % and in SLC7A9 gene for 30.6 % of the cystinuric chromosomes. Ten different mutations in SLC3A1 gene were found, and two of them were novel (C242R and L573X), while in SLC7A9 gene seven mutations were found, of which three were novel (G73R, V375I and c.1048_1051delACTC). The most common mutations in this study were T216M (24.5 %), M467T (16.3 %) and R365L (11.2 %) in SLC3A1 and G105R (21.4 %) in SLC7A9 gene. A population specificity of cystinuria mutations was observed; T216M mutation was the only mutation present among Gypsies, G105R was the most common mutation among Albanians and Macedonians, and R365L among Serbs. The results of this study allowed introduction of rapid, simple and cost-effective genetic diagnosis of cystinuria that enables an early preventive care of affected patients and a prenatal diagnosis in affected families.