Vitamin D deficiency rickets mimicking pseudohypoparathyroidism

Vitamin d deficiency rickets (vddr) is a disorder biochemically characterized by elevated serum alkaline phosphatase (alp) activity,normal or decreased serum calcium (ca) and inorganic phosphate concentrations,secondary hyperparathyroidism and decreased serum 25-hydroxyvitamin d (25(oh)d) levels. in stage 1 vddr,urinary amino acid and phosphate excretion are normal with minimal or no findings of rickets on radiographs. pseudohypoparathyroidism (php) is an inherited disorder characterized by end-organ resistance to parathormone (pth). vddr occasionally resembles php type 2 in clinical presentation and biochemical features,creating difficulties in the differential diagnosis of these two entities. here we report an infant diagnosed with vddr. in addition to inadequate vitamin d intake,usage of antiepileptic drugs (aed) may have led to the worsening of the vitamin d deficiency. the patient presented with a history of febrile convulsions,for which he received phenobarbital treatment. the initial findings of hypocalcemia,hyperphosphatemia and normal tubular reabsorption of phosphate,mimicking php 2,responded well to vitamin d and oral ca treatment with normalization of serum ca,phosphorus (p),alp and pth levels. © journal of clinical research in pediatric endocrinology.