Abstract 170: Short stature and rickets due to proximal renal tubular acidosis: A series of four distinct etiologies

Introduction: Rickets due to renal tubular acidosis is not uncommon, but rarely diagnosed. We describe four cases of proximal renal tubular acidosis presenting with short stature and rickets. After excluding nutritional, calcipenic and commoner causes of rickets, proximal renal tubular dysfunction was diagnosed in all cases. Case 1: Our first case is a 7-year-old boy with pathological fracture, protuberant abdomen and radiological features of rickets. The boy had phosphaturia, glucosuria, and proteinuria. Genetic testing confirmed a diagnosis of Fanconi- Bickel syndrome with mutation in SLC2A2. He is on phosphate and calcitriol replacement. Case 2: The second case is that of a short girl with lower limb deformity. She had phosphaturia, metabolic acidosis, aminoaciduria hypokalaemia, crystals on the cornea and hypothyroidism. Leucocyte cysteine levels were elevated. Genetic analysis revealed nephropathic cystinosis. Case 3: The next case is a 2-year-old female presenting with delayed development, polyuria and widening of wrists and ankles. There was profound hypophosphatemia, phosphaturia, metabolic acidosis, glucosuria, aminoaciduria and multiple liver nodules on Ultrasonography. Mass spectrometry analysis of blood and urine gave a diagnosis of tyrosinemia type1. Case 4: Our fourth case is 10-year-old boy presenting with diminution of vision and short stature. There was severe metabolic acidosis with adequate urinary acidification and delayed bone age. Eye examination showed a band shaped corneal opacity in both eyes. The overall picture was suggestive of Sodium bicarbonate cotransporter (NBC) defect in the proximal tubule. [INLINE:1] Discussion: These cases represent four rare and difficult to diagnose causes of short stature and rickets due to proximal renal tubular involvement. Short stature, metabolic acidosis, varying degrees of proximal tubular defect are common to all these cases with unique overtones. Renal phosphate wasting is seen in most. Oral phosphate, active vitamin D3, alkali form the cornerstone of management with individualisations.