Endocrine Abstracts

Case history: A 28 year-old male of British origin was referred with a one-year history of a left-sided chest mass and an abnormal chest X-ray. He was otherwise fit and well, had a past medical history of vitiligo and had no relevant family history. His physical examination revealed some hypopigmented spots on his skin, several tattoos across his back and a firm mass on his left upper chest, which was mildly tender on palpation. He had no other palpable masses.

Investigations: Laboratory investigation revealed hypercalcaemia (adjusted serum calcium 2.63 mmol/l), an elevated parathyroid hormone (PTH 8.0 pmol/l), elevated bone markers (alkaline phosphatase 479 U/l, N-terminal propeptide of type 1 collagen 616 mcg/l) and a low vitamin D (9.1 nmol/l). Cross sectional imaging with computed tomography and whole body magnetic resonance imaging (MRI) showed multiple heterogenous tumorous areas involving the left superior pubic ramus, left acetabulum, left iliac bone, right clavicle as well as ribs bilaterally. The largest of these lesions was centred in the left 3^rd rib and corresponded to the patient’s palpable mass. Biopsy of this larger mass showed morphological features consistent with a brown tumour of hyperparathyroidism. Parathyroid scintigraphy revealed a hot spot that was thought to represent a parathyroid adenoma.

Results and treatment: The diagnosis of brown tumour of hyperparathyroidism secondary to a parathyroid adenoma was made and the patient underwent a targeted parathyroidectomy with histological confirmation of an adenoma. His post-operative bloods showed normal adjusted calcium and PTH levels, but worsening bone markers. MRI repeated serially to 3 years after the operation showed the bone lesions were increasing in size, instead of regressing, as might have been expected of a brown tumour. The initial biopsy was subsequently reviewed and found to show fibrous dysplasia with diffuse aneurismal bone cyst-like change. Genetic testing confirmed the diagnosis of polyostotic fibrous dysplasia. The patient has been managed conservatively and remains pauci-symptomatic.

Conclusions and points for discussion: We present a case of polyostotic fibrous dysplasia associated with primary hyperparathyroidism, which is the least frequent endocrinopathy in fibrous dysplasia. Whether hyperparathyroidism was a result of the genetic changes present in fibrous dysplasia or whether it was a mere coincidence for them to present in the same patient remains uncertain. The role of bisphosphonates in the management of these patients is controversial although we have concern over the proximity of this expanding bone lesion to the heart.