MON-357 Craniofacial Deformities with Hypercalcemia: A Rare Case of Co-Existing Primary Hyperparathyroidism and Paget’s Disease of the Bone Since Young Adulthood

Background: Primary Hyperparathyroidism (PHPT) and Paget’s Disease of the Bone (PDB) are two distinct bone mineral disorders which rarely co-exist. It has been very scarcely reported in the elderly but almost unheard of in young adults. Clinical case A middle-aged Indian lady presents with multiple and recurrent facial and jaw bony swellings, since the age of 12. She had normal developmental as a child, without visual, auditory deficits or limb deformities. No family history of hypercalcemia or endocrine disorders was elicited. At initial diagnosis, biochemical parameters were consistent with PHPT, with mild to moderate hypercalcemia (2.6-3.0 mmol) and concomitant hypophosphatemia (0.6-0.8 mmol/L), elevated intact PTH 10.6pmol/L and ALP persistently more than 350 U/L. She had undergone multiple surgeries to remove the bony swellings, presumed to be brown tumours. She developed medullary nephrocalcinosis approximately 30 years after onset of illness. Over a span of three decades, numerous modalities were employed in attempt to localise the parathyroid lesion, including imaging (ultrasonography, sestamibi with SPECT CT, FDG PET),angiography, venous sampling and exploratory neck surgeries which were unsuccessful. Due to failure in localising the offending parathyroid lesion, it was conceded to maintain her on medical therapy.She was initially started on oral phosphate therapy, intranasal calcitonin and subsequently calcimimetics. Aside from rising ALP levels, her other biochemical parameters remained static. Her diagnosis was re-evaluated when she presented with osteomyelitis of the right mandible requiring surgery. Pre -operative CT imaging showed mixed lytic and sclerotic lesions at the mandible, maxilla, facial bones and skull. It also revealed diffuse thickening of the calvarium with narrowing of the posterior fossa resulting in hydrocephalus, requiring a ventriculoperitoneal shunt insertion. Histopathological examination of the mandible showed a background of osteosclerosis. These findings were inconsistent with PHPT and was most often described in PDB. On the other hand, a repeated skeletal survey showed generalised osteopenia in the small bones of the hand with subperiosteal and terminal phalanges reabsorption which was in keeping with PHPT. Her pelvis, spine and long bones remained normal and bone densitometry was preserved. It was concluded that this patient was suffering from dual pathology, PHPT and PDB and was commenced on bisphosphonates. Conclusion: This lady presented with two diseases which simulate each other despite not being etiologically linked. The aberrancy in the age of onset and the overlapping clinical features of the dual pathology imposed a significant challenge in making the correct diagnosis. Retrospectively, histopathological examination of the bone at an earlier stage of disease may have been the key to solving this perplexing case.