Endocrine Abstracts

Introduction: Distal renal tubular acidosis (RTA) can have varied presentation. Onset in infancy is usually severe. However, adolescent onset has variable presentation ranging from hypokalemia to nephrocalcinosis, and rarely with rickets or growth retardation. We describe a girl with distal RTA presenting with hypokalemia and growth retardation.

Case: 12 year old girl presented with recurrent episodes of weakness of all four limbs and failure to gain height and weight for last 4 years. There was no sensory or autonomic involvement. She had normal birth history and developmental milestones, no dysmorphism or bony abnormality, no sensorineural deafness and a negative family history. Nutritional status was average. Height and weight were below Indian Academy Of Paediatrics 3rd percentile.

Investigations: K⁺=2.9 mmol/l; Urine K=30 mmol/24 hr (increased). pH=7.324, HCO3^-=12.4 meq/l, pCO₂ =23.9 mm-Hg; anion gap=10 mmol/l Urine pH =7.0. UAG: Positive (28 meq/l), urine calcium:creatinine ratio=0.63(N<0.2) ANA & ENA: negative. Genetic testing not done due to non-availability CBC, LFT, serum 25-OH Vitamin D & iPTH, Ca⁺⁺, PO₄^3-, alkaline phosphatase, FT4/TSH, IGF-1 were all normal. X-ray of wrist: no evidence of rickets. USG Abdomen =Medullary Nephrocalcinosis in both kidneys.

Diagnosis: Growth retardation with hypokalemic periodic paralysis in a case of distal RTA of adolescent onset based on normal anion gap acidosis with high urinary pH with positive urine anion gap.

Treatment: She was managed successfully with intravenous potassium and is on oral sodium bicarbonate 500 mg twice daily. Her clinical response is good.

Conclusion: The take home points are that every child presenting with hypokalemia should be evaluated for RTA. The presentation of distal RTA can be subtle to severe. Even in the absence of bony involvement like rickets children can suffer from significant growth retardation. Growth failure should be actively searched for even in asymptomatic patients.