Introduction: Primary hyperparathyroidism (PHPT) is a common disorder that typically leads to increased bone turnover and reduced bone mineral density (BMD). Osteopetrosis, in contrast, is a rare, inherited disorder of defective osteoclast function, resulting in diffusely sclerotic but structurally fragile bones. The coexistence of both conditions is rare and can significantly alter the expected skeletal phenotype of PHPT. Case: We report a 77-year-old female with a previous history of resected ovarian carcinoma in remission, chronic iron deficiency anemia, and hypothyroidism. During a hospital admission for a lacunar infarct, an incidental finding of sclerotic skull lesions on computed tomography (CT) brain prompted further investigation. She had no history of fractures, hearing impairment, or family history of parathyroid or bone disorders. Biochemistry revealed parathyroid-dependent hypercalcemia with normal renal function. Bone turnover markers showed a normal resorption marker (BCTx) but an elevated formation marker (P1NP), with a mildly raised alkaline phosphatase. A sestamibi scan localized a probable left upper parathyroid adenoma, despite a negative neck ultrasound. Skeletal survey unexpectedly revealed widespread osteosclerosis of the skull, spine, and long bones, with a markedly elevated BMD on densitometry. Review of prior imaging confirmed that these sclerotic changes predated her current presentation, having been present on CTs from over a decade ago. Recurrent malignancy was excluded with repeat imaging and tumor markers. A diagnosis of PHPT secondary to parathyroid adenoma, coexisting with underlying, previously unrecognized osteopetrosis, was made. The patient declined both recommended parathyroidectomy and genetic studies. Conclusion This case demonstrates a rare coexistence of two pathologies with opposing effects on bone metabolism. The underlying osteopetrosis, characterized by defective osteoclasts, likely rendered the patient’s osteoclasts resistant to the catabolic effects of elevated PTH. This resulted in an atypically normal bone resorption marker and an unexpectedly high BMD, despite the diagnosis of PHPT.
Bone Density' ; Hyperparathyroidism ; Primary Osteopetrosis