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Clinical and genetic characterization of Chinese pediatric cystine stone patients
Luming Shen1, Xiaoming Cong1, Xin Zhang1
1Department of Urology, Jiangsu Province Hospital of Traditional Chinese Medicine, Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing, PR China.
Insights
Chinese pediatric cystinuria patients often develop recurrent cystine stones and may face impaired renal function. This study identified novel gene mutations and frequent metabolic abnormalities, highlighting genetic heterogeneity in this population.
Area of Science:
- Nephrology
- Genetics
- Pediatrics
Background:
- Cystinuria is an autosomal recessive disorder characterized by cystine stone formation.
- Clinical and genetic presentations of cystinuria vary globally.
- Understanding these variations is crucial for effective patient management.
Purpose of the Study:
- To characterize Chinese pediatric patients with cystine stones.
- To investigate genetic mutations in SLC3A1 and SLC7A9 genes.
- To identify associated metabolic abnormalities.
Main Methods:
- Evaluation of 13 pediatric cystine stone patients and 13 pediatric calcium oxalate stone controls.
- Genetic analysis of SLC3A1 and SLC7A9 gene mutations.
- Comprehensive metabolic evaluation of urinary and serum parameters.
Main Results:
- 17 distinct missense mutations were identified in SLC3A1/SLC7A9, with 12 being novel.
- 77% of cystine stone patients exhibited metabolic abnormalities, primarily hyperoxaluria, hypercalciuria, and hypocitraturia.
- Cystine stone patients presented with more bilateral stones, larger stone size, and higher serum BUN/Cr compared to controls.
Conclusions:
- Cystinuria patients face risks of recurrent stones, impaired renal function, and potentially calcium oxalate stone formation.
- Novel gene mutations were identified, suggesting genetic and allelic heterogeneity in Chinese pediatric cystinuria.
- Frequent metabolic abnormalities underscore the need for tailored diagnostic and therapeutic approaches.
Introduction:
Cystine stone is the only clinical manifestation in patients with cystinuria, which is an autosomal recessive inheritable disease. However, clinical and genetic data vary among patients in different countries.
Objective:
To investigate the characteristics of Chinese pediatric cystine stone patients.
Patients And Methods:
Thirteen pediatric patients with cystine stones were evaluated in our clinic between 2012 and 2015. Gene mutations in SLC3A1 and SLC7A9 were investigated. Metabolic evaluation was also performed. Thirteen pediatric patients with calcium oxalate stones were selected as controls.
Results:
Of these patients, eight were males and five were females. Average age at detection of the first stone was 6.8 ± 5.2 years. Urinary stones in three of the 13 cystine patients were composed of cystine and calcium oxalate. The 63.6% of patients with upper urinary stones had bilateral stones. A total of 17 different missense mutations were identified, and 12 of these mutations were first reported in this study. Metabolic abnormalities could be detected in 77% of cystine stone patients. The most common metabolic abnormality was hyperoxaluria, followed by hypercalciuria and hypocitraturia. Compared with calcium stone patients, our cystine stone patients had a higher rate of bilateral stones, larger stone size, higher levels of serum BUN and Cr, urine citrate excretion (Table), and higher mean value of surgeries per patient. By contrast, the opposite was true for urine oxalate excretion and AP (CaOx) index EQ. The urine excretion of cystine was not correlated with other urinary constituents.
Discussion:
Patients with cystinuria frequently suffer recurrent renal stones and may subsequently need a series of stone removal procedures during their lifetime. This condition is likely to affect their overall renal function. SLC3A1 and SLC7A9 have been extensively investigated, but a detection rate of 100% in cystinuric patients has yet to be obtained. In our study, we found 14 missense mutations in 18 of 26 alleles except four mutation polymorphisms. Most of the gene mutations found in our study were their first reports. Metabolic abnormalities were frequently found in cystine stone patients, but their risk of calcium oxalate stone formation was relatively lower than that of patients with calcium oxalate stones.
Conclusions:
Cystine stone patients are at risk of impaired renal function and the formation of calcium oxalate stones. Most of the gene mutations identified in our patients were first reported in this study. Therefore, cystinuria possibly exhibits genetic and allelic heterogeneity in Chinese pediatric cystine stone patients.
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