Hypercalcaemia is a common clinical scenario in Paediatric Endocrinology. We report a case of a delayed diagnosis of parathyroid adenoma in the presence of vitamin D and dietary calcium insufficiency.
A 12-year-old boy, a refugee from Sudan, was referred for evaluation of an incidental finding of asymptomatic hypercalcemia. He was previously treated for tuberculosis. He also had lactose intolerance with significantly restricted dietary calcium intake. There was no family history of hypercalcaemia or endocrine neoplasia. He had normal growth with dark skin complexion and a normal systemic examination.
His initial investigations showed significant hypercalcaemia (corrected calcium 3.27 mmol/l), normal phosphate level with elevated PTH. He had moderate Vitamin D deficiency with high alkaline phosphatase (ALP). There was no radiological evidence of rickets nor subperiosteal bone resorption. The two main differential diagnoses at this stage were primary hyperparathyroidism (PHPT) or familial hypocalciuric hypercalcaemia (FHH) with concomitant vitamin D deficiency. There was no nephrocalcinosis nor evidence of parathyroid adenoma on ultrasound. His initial 24 hour urine calcium excretion showed hypocalciuria raising the possibility of familial hypocalciuric hypercalcaemia. Parental calcium status was unknown as the biological parents were deceased.
He was lost to follow up but represented with persistent hypercalcaemia with further elevation of PTH although he remained asymptomatic. His vitamin D level normalized with treatment but his ALP and PTH remained elevated. His subsequent urine calcium: creatinine ratio showed hypercalciuria and neck ultrasound revealed a left inferior parathyroid adenoma. A focused parathyroidectomy confirmed benign parathyroid adenoma. His ALP normalized after parathyroidectomy. A genetic panel was negative for MEN1, RET, and CDC73 mutations.
This case illustrates how early biochemical manifestations of parathyroid adenoma could be masked by concomitant Vitamin D and dietary calcium deficiency highlighting the importance of follow up and further review to establish the correct diagnosis.