Distal Renal Tubular Acidosis: A Conundrum of Short Stature, Failure to Thrive, Rickets, and Nephrocalcinosis

Distal renal tubular acidosis (dRTA) is an uncommon disorder marked by defective hydrogen ion excretion in the distal nephron, leading to hyperchloremic metabolic acidosis, persistently alkaline urine, and hypokalemia. Chronic, untreated dRTA in children often presents with growth failure, refractory rickets, and nephrocalcinosis, yet is frequently misdiagnosed. We report a 13-year-old girl with severe stunting, bone pain, proximal muscle weakness, and polyuria for several years. Examination revealed significant short stature, malnutrition, widened wrists, a protuberant abdomen, and genu valgum. X-rays demonstrated classical rachitic changes. Biochemical investigations showed severe hypokalemia (1.3 mEq/L) and metabolic acidosis (pH 7.22, HCO₃- 7.6 mmol/L) with an inappropriately alkaline urine pH of 6.6. Imaging confirmed medullary nephrocalcinosis. A diagnosis of idiopathic distal renal tubular acidosis (RTA) was made. She was treated with oral alkali and potassium supplements. Over three months, acidosis improved (HCO₃- 18 mmol/L), potassium normalized (3.2 mEq/L), and X-rays showed healing of rickets. Significant catch-up growth was noted, with a 10 cm height gain and 5 kg weight gain at six months. This case highlights the importance of considering dRTA in children with unexplained growth failure or rickets unresponsive to standard therapy. The classic triad - normal anion gap metabolic acidosis, hypokalemia, and alkaline urine - should prompt evaluation for dRTA. The treatment response with affordable alkali therapy is also highlighted, resulting in miraculous improvement in the patient.