Etiology and outcomes of primary renal tubular acidosis.

BACKGROUND

This study investigates the etiology, outcomes, and genotype-phenotype correlations in patients with renal tubular acidosis (RTA) at a tertiary care center in New Delhi.

METHODS

This cross-sectional study included children and young adults with RTA who underwent clinical, biochemical, radiological and/or genetic evaluations between July 2020 and December 2024. We report clinical phenotype, anthropometry, metabolic control and progression to chronic kidney disease (CKD) in relation to genotype of distal RTA.

RESULTS

Of 135 patients enrolled, 69 had distal RTA. The yield of genetic testing was 72% in distal RTA and 88.7% in Fanconi syndrome. Variants in SLC4A1 (42.4%) and ATP6V1B1 (28.8%) were the most common etiologies of distal RTA. Compared to other etiologies, patients with SLC4A1 variants were older at symptom onset (P = 0.008). Hematological abnormalities were more frequent in patients with biallelic compared to heterozygous SLC4A1 variants (50% vs. 12.5%; P = 0.18). Nephrocalcinosis and metabolic control were similarly prevalent across genetic categories of distal RTA. Sensorineural hearing loss was more common with ATP6V1B1 than with ATP6V0A4 variants (61.5% vs. 22.2%, P = 0.099) and did not vary by metabolic control. At median follow-up of 5-years, 74.1% of patients with distal RTA had short stature, 74.6% had poor metabolic control and 2.9% had progressed to CKD G3-5.

CONCLUSIONS

This study outlines the genetic etiology and phenotype of distal RTA in south Asia. Over short-term follow-up, poor metabolic control and severe stunting were common, while CKD was uncommon.