Clinical and genetic analysis of distal renal tubular acidosis in three Chinese children

Abstract

Objective: Primary distal renal tubular acidosis (dRTA) is a rare genetic disease characterized by distal tubular dysfunction leading to metabolic acidosis and alkaline urine. Growth retardation is a major concern in these children. The disease is caused by defects in at least three genes (SLC4A1, ATP6V0A4, and ATP6V1B1) involved in urinary distal acidification. Several series of dRTA patients from different ethnic backgrounds have been genetically studied, but genetic studies regarding Chinese population is rare. Our aim was to investigate the clinical features and genetic basis of primary dRTA in Chinese children.

Methods: Three unrelated patients with dRTA participated in our study. Next-generation sequencing was performed, and the findings were validated using the Sanger sequencing method.

Results: All patients exhibited hyperchloraemic metabolic acidosis, abnormally high urine pH, hypokalemia, and nephrocalcinosis. Growth retardation was observed in all patients. During the follow-up (range 1-4 years), alkali replacement therapy corrected the systemic metabolic acidosis, and two patients demonstrated normal growth. rhGH therapy was administered to patient-3 at the age of 6 years, and his growth rate was significantly improved (growth velocity 9.6 cm/yr). In total, 5 mutations were identified in our cohort of three patients, and four mutations were novel.

Conclusions: We report the clinical and molecular characteristics of dRTA patients from China. The four novel mutations detected in our study extend the spectrum of gene mutations associated with primary dRTA. Furthermore, our study confirms the effect of early treatment in improving growth for dRTA patient and provides insight into the effects of rhGH on dRTA patients who were diagnosed late and exhibiting a persistent growth delay despite appropriate therapy.

Keywords: ATP6V0A4; ATP6V1B1; SLC4A1; distal renal tubular acidosis; growth; recombinant human growth hormone.

Figure 1.

Growth condition before and after rGH therapy in patient-3. Source: Child Growth Standards (0–5 years), 2006, World Health Organization. Growth Reference (5–19 years), 2007, World Health Organization.

Figure 2.

Results of sequencing for the c.1418C > T and c.2419C > T mutations in ATP6V0A4 in family-1.

Figure 3.

Results of sequencing for the c.409C > T and c.904C > T mutations in ATP6V1B1 gene in family-2.

Figure 4.

DNA sequencing profile of the c.1766C > T mutation in SLC4A1 gene in family-3.