A rare case of congenital distal renal tubular acidosis combined with medullary sponge kidney.

Distal renal tubular acidosis combined with medullary sponge kidney (MSK) is not uncommon in adults, but is rare in infants. We report a 13-month-old boy with MSK who had features of distal renal tubular acidosis (nephrocalcinosis, hypercalciuria, hypocitraturia) and failed to thrive. Renal ultrasound revealed bilateral increased medullary echogenicity and nephrocalcinosis. Bilateral medullary nephrocalcinosis in the ultrasound was the first sign that alerted our pediatrician to the presence of MSK in infants. Earlier treatment may increase efficacy.