Primary hyperparathyroidism: a rare cause of genu valgus in adolescence

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.

Alkaline phosphatase in pediatric patients with genu varum caused by vitamin D-deficient rickets

An elevated serum alkaline phosphatase (ALP) level is one of the markers for the presence of rickets in children, but it is also associated with bone formation. However, its role in diagnosing genu varum in pediatric patients with vitamin D-deficient rickets is still unknown. To clarify the role of the serum ALP level in assessing the severity of genu varum, we retrospectively investigated this issue statistically using data on rickets such as serum intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, ALP, the level of creatinine as the percentage of the median according to age (%Cr), and the metaphyseal diaphyseal angle (MDA) in the lower extremities as an index of the severity of genu varum. A multiple regression analysis revealed that log ALP and %Cr values were negatively associated with MDA values. The former association was also confirmed by a linear mixed model, while iPTH was positively associated with MDA by path model analysis. To elucidate the association of ALP with MDA in the presence of iPTH, we investigated three-dimensional figures by neural network analysis. This indicated the presence of a biphasic association of ALP with MDA: the first phase increases while the second decreases MDA. The latter phenomenon is considered to be associated with the increase in bone formation due to the mechanical stress loaded on the lower extremities. These findings are important and informative for pediatricians to understand the significance of the serum ALP level in pediatric patients with genu varum caused by vitamin D deficiency.

Bilateral Genu Valgum in an Adolescent with Primary Hyperparathyroidism: A Case Report and Review of Literature

Primary hyperparathyroidism in children and adolescents is rare and often symptomatic at presentation. A 15-year-old bo presented with bilateral genu valgum for two years. Biochemical results were consistent with primary hyperparathyroidism Calcium levels normalized two months after removal of a left inferior parathyroid adenoma.