A Diagnosis of Normocalcemic Primary Hyperparathyroidism Prompted by “Salt and Pepper” Lesions of the Calvarium

BACKGROUND: We report a case of normocalcemic primary hyperparathyroidism, a diagnosis prompted by radiographic “salt and pepper” calvarial lesions, typically described in hypercalcemic primary hyperparathyroidism or secondary hyperparathyroidism. CASE REPORT: A 60-year-old woman noticed indentations of her scalp and presented to her primary care provider. Radiography of the calvarium demonstrated granular “salt and pepper” lesions, prompting investigation. The patient was found to have an elevated parathyroid hormone (PTH) level of 79 pg/mL (reference range, 14-54 pg/mL) and a normal albumin-corrected calcium level of 9.8 mg/dL (reference range, 8.6-10.4 mg/dL). She was referred to our endocrine clinic and described having bone aches, fevers, leg cramps, and a remote history of nephrolithiasis. Her physical examination revealed hypertension. Repeat laboratory evaluation confirmed elevated PTH and normal albumin-corrected calcium. Secondary causes of hyperparathyroidism were ruled out. Her 25-hydroxyvitamin D level was 35 ng/mL (reference range, 30-100 ng/mL), with a normal creatinine level (0.73 mg/dL; reference range, 0.5-0.99 mg/dL). The patient underwent ultrasound and sestamibi scintigraphy, with uptake in the right inferior thyroid pole. She was found to have a 6-mm parathyroid adenoma and underwent a targeted parathyroidectomy, with normalization of serum PTH. DISCUSSION: Many cases of normocalcemic primary hyperparathyroidism are diagnosed in asymptomatic patients presenting with low bone mass; however, imaging prompted this patient's evaluation. Ultimately, the calvarial lesions were thought secondary to bone resorption from increased osteoclast activity. CONCLUSION: This case highlights an atypical presentation of normocalcemic primary hyperparathyroidism in that the evaluation was precipitated by unexpected radiographic evidence of metabolic bone disease, rather than by symptoms or biochemical studies.