Bartter Syndrome-Related Variants Distribution: Brazilian Data and Its Comparison with Worldwide Cohorts

Abstract

Background: Genetic testing is recommended for accurate diagnosis of Bartter syndrome (BS) and serves as a basis for implementing specific target therapies. However, populations other than Europeans and North Americans are underrepresented in most databases and there are uncertainties in the genotype-phenotype correlation. We studied Brazilian BS patients, an admixed population with diverse ancestry. Methods: We evaluated the clinical and mutational profile of this cohort and performed a systematic review of BS mutations from worldwide cohorts. Results: Twenty-two patients were included; Gitelman syndrome was diagnosed in 2 siblings with antenatal BS and congenital chloride diarrhea in 1 girl. BS was confirmed in 19 patients: BS type 1 in 1 boy (antenatal BS); BS type 4a in 1 girl and BS type 4b in 1 girl, both of them with antenatal BS and neurosensorial deafness; BS type 3 (CLCNKB mutations): 16 cases. The deletion of the entire CLCNKB (1–20 del) was the most frequent variant. Patients carrying the 1–20 del presented earlier manifestations than those with other CLCNKB-mutations and the presence of homozygous 1–20 del was correlated with progressive chronic kidney disease. The prevalence of the 1–20 del in this BS Brazilian cohort was similar to that of Chinese cohorts and individuals of African and Middle Eastern descent from other cohorts. Conclusion: This study expands the genetic spectrum of BS patients with different ethnics, reveals some genotype/phenotype correlations, compares the findings with other cohorts, and provides a systematic review of the literature on the distribution of BS-related variants worldwide.