Primary Hyperparathyroidism: A Rare Cause of Genu Valgus in Adolescence

A 15-year-old girl presented with a history of progressive genu valgus of both lower limbs. She had no other skeletal deformities or fractures. There was no significant family history, in particular none to suggest multiple endocrine neoplasia syndrome. Radiographs of the lower limbs confirmed severe bilateral genu valgus (Figure 1). Investigations revealed a markedly elevated serum corrected calcium of 12.4 mg/dL (normal, 8.8–10.4), phosphate of 2.8 mg/dL (normal, 3.4–5.8), alkaline phosphatase of 1136 IU/L (normal, 50–136), intact PTH of 1649 pg/ml (normal, 10–68), 25-hydroxyvitamin D of 28 ng/ml (normal, 9–52), and 24-hour urinary calcium of 196 mg/d (normal, 88–300). Further radiographs of the hand re-