Parathyroid Carcinoma Mimicking Multiple Myeloma: A Tale of Refractory Hypercalcemia

Primary hyperparathyroidism yields various symptoms, including hypercalcemia, pathological fracture, and renal impairment. Parathyroid carcinoma is the rarest cause of primary hyperparathyroidism, accounting for <1% of the cases. We reported a case of a 46-year-old male with closed fractures at the humerus and femur. Further findings revealed severe refractory hypercalcemia, renal impairment, anemia, and bone lytic lesion (CRAB). No palpable cervical mass was identified. Surprisingly, the serum protein electrophoresis was normal, and urinary Bence-Jones protein was negative along with normal bone marrow aspiration. Hence, multiple myeloma was unlikely. The intact parathyroid hormone level was very high, along with a suspicious nodule on the left thyroid lobe (TIRADS 4). Total thyroidectomy and total parathyroidectomy were performed. The post-surgical pathological examination confirmed the diagnosis of parathyroid carcinoma. After the surgery, the patient was in stable condition with normal intact parathyroid hormone and serum calcium levels. In this case, primary hyperparathyroidism was caused by parathyroid carcinoma with “CRAB” symptoms, mimicking multiple myeloma. Primary hyperparathyroidism should be considered in the patient with refractory hypercalcemia.