Primary hyperparathyroidism in an adolescent presenting with genu valgus progressing to extensive bone disease; a case report

BACKGROUND: Primary hyperparathyroidism which is rare in adolescents presents commonly with non-specific symptoms and systemic complaints. Though there are few reported cases of genu valgus, genu valgus progressing to extensive bone disease despite mildly elevated calcium had not been reported before. CASE PRESENTATION: A 12-year-old male had been evaluated for bilateral (left > right) genu valgus and short stature. Serum calcium and phosphate levels had been normal. X-ray of the femora and pelvic bones had not shown additional abnormalities. Valgus deformity progressed despite left femoral plating, and a left distal femoral medial closed wedge osteotomy had been performed at 15 years. Plain imaging at that time had shown localised osteopaenia. At the age of 17 years, he developed multiple fragility fractures of his left hip rendering him wheelchair-bound. Further evaluation revealed a serum PTH level of 2571 (10–65) pg/mL with calcium of 2.82 (2.2–2.6) mmol/L and inorganic phosphate of 1.7 (2.2–4.7) mg/dL. The lumbar spine DXA scan showed a Z-score of -5.8. A left parathyroid adenoma was localised and there was evidence of hyperparathyroid bone disease including brown tumours. He underwent left parathyroidectomy and left thyroid lobectomy after which his PTH level dropped to 4.03 pg/mL. He developed hypocalcaemia which was managed successfully with calcium and alfacalcidol replacement. CONCLUSIONS: Primary hyperparathyroidism can present with genu valgus in adolescents. Initial normocalcaemia which could be due to concomitant vitamin D deficiency could mask this leading to delayed diagnosis until severe irreversible bone disease ensues.