Normocalcemic Primary Hyperparathyroidism Presenting with Muscle Weakness and Body Pain

We herein report a 39-year-old woman who had aggravated body pain, waddling gait, and fatigability for the past 2 years. A neurological examination showed hyperreflexia and proximal muscle weakness. The serum calcium level was normal (10.1 mg/dL). However, serum alkaline phosphatase (3,855 IU/I) and parathyroid hormone (1,008 pg/mL) levels were remarkably high. Cervical ultrasonography revealed parathyroid goiter. The patient was diagnosed with hyperparathyroidism. Her muscle weakness and pain improved within three months after parathyroidectomy. Our findings suggest that clinicians should consider hyperparathyroidism as a differential diagnosis in patients with proximal muscle weakness, even if the serum calcium level is normal.