Primary Hyperparathyroidism Presenting with Multiple Lytic Lesions: A Case Report

Primary Hyperparathyroidism (PHPT) is a condition characterised by elevated serum calcium levels along with elevated serum Parathyroid Hormone (PTH). The main cause of PHPT is parathyroid adenoma or parathyroid gland hyperplasia. Symptoms and signs of this condition may mimic those of the first differential diagnoses, such as multiple myeloma or metastatic disease from a primary source. In this case, a lady presented with progressively increasing lower back pain and difficulty walking. Initially, the clinical diagnosis leaned towards multiple myeloma or metastatic disease of unknown origin based on Positron Emission Tomography-Computed Tomography (PET-CT) findings. However, her serum calcium levels remained persistently elevated, while her serum phosphorus levels were normal. Consequently, a serum PTH level test indicated elevated levels. A biopsy from an Fluorodeoxyglucose (FDG)-avid lytic lesion in the left iliac bone showed a giant cell-rich lesion that was positive for CD 163 and Vimentin by Immunohistochemistry (IHC), favouring a diagnosis of brown tumour of the bone. A subsequent surgical excision of the adenoma, along with the parathyroid gland, was performed. The patient received intravenous bisphosphonate therapy for the lytic lesion and was advised to follow up every three months with serum calcium and PTH levels monitored.