Endocrine Abstracts

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, progression to extensive bone disease with fractures has not been commonly reported. Additionally, hypercalcaemia at the time of presentation was almost universal.

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 alkaline phosphatase level was 4785 IU/l and the vitamin D level was 24.96 ng/ml. The lumbar spine DXA scan showed a Z-score of -5.8. Diffusely scattered lytic bone lesions with associated bone expansion suggestive of brown tumours of hyperparathyroid bone disease were noted in the CT scan of humeri. There were no features of rickets. A left parathyroid adenoma measuring 51×30x16 mm was localised. He underwent left parathyroidectomy and left thyroid lobectomy after which his PTH level dropped to 4.03 pg/ml. Histology confirmed a benign parathyroid adenoma. He developed hypocalcaemia which was managed successfully with calcium and alfacalcidol replacement. Three months after the surgery, his alkaline phosphatase level dropped to 380 IU/l.

Conclusions: Cases of adolescents presenting with genu valgus due to primary hyperparathyroidism have been reported before. However, fractures and severe bone disease are exceedingly rare. Initial normocalcaemia, probably related to concomitant vitamin D deficiency could have masked the diagnosis leading to delayed diagnosis and extensive irreversible bone disease. High-index of suspicion and close surveillance is warranted in atypical presentations to avoid a delayed diagnosis of underlying metabolic disease.