Hereditary Distal Renal Tubular Acidosis with Subclinical Hypothyroidism: A Case Report of Slc4a1 Mutation

Abstract

Background: Distal renal tubular acidosis (dRTA) is a rare disorder characterized by impaired acid secretion in the distal nephron. Hereditary variants are infrequent in children, especially those caused by SLC4A1 mutations.

Case Presentation: A  5-year-old developmentally normal girl child born to non-consanguineous parents presented with faltering growth, leg pain, polyuria, polydipsia, and preference for salty foods. Investigations revealed severe metabolic acidosis, hypokalemia, hypercalciuria with alkaline urine and subclinical hypothyroidism. Ultrasound showed bilateral medullary nephrocalcinosis. Suspecting dRTA and primary hyperoxaluria, whole exome sequencing was performed which revealed a homozygous pathogenic variant in the SLC4A1 gene [c.2573C>A (p.Ala858Asp)], confirming autosomal recessive hereditary dRTA. Following treatment with potassium citrate, hydrochlorothiazide and pyridoxine, child showed catch-up growth and improved biochemical parameters during six-month follow-up period.

Conclusion: This case emphasizes the importance of considering hereditary dRTA in children with nephrocalcinosis and growth failure. Genetic confirmation aids in early detection, focused treatment and family counselling.