Thyroid disease-related false-negative ultrasonography and 99mTc-MIBI scintigraphy in primary hyperparathyroidism: a case report and literature review.

Background: Multiple gland disease associated with primary hyperparathyroidism (PHPT) are relatively rare, and those combined with underlying thyroid diseases are even rarer. This study aimed to investigate the approaches to preoperative localization and enumeration of lesions, as well as the determination of surgical endpoints in such patients. Case Description: A female patient was admitted due to "elevated serum calcium detected for more than 20 days", with a past medical history of hyperthyroidism and Hashimoto's thyroiditis. Neck ultrasound only suggested a single-gland lesion, and 99mTc-MIBI scintigraphy demonstrated unremarkable findings. Subsequent contrast-enhanced computed tomography (CT) revealed enlarged parathyroid glands posterior to both lobes of the thyroid gland. Preoperative diagnosis was PHPT with suspected multiglandular disease. Bilateral cervical exploration and parathyroidectomy were performed. Intraoperatively, two enlarged parathyroid glands were identified, located posterior to the upper pole of the left thyroid lobe and in the right central compartment respectively. Postoperative pathology confirmed nodular hyperplasia of the parathyroid glands in both lesions. Conclusions: In patients with multiple gland disease associated with PHPT complicated with underlying thyroid diseases, identification of the location and number of lesions is more challenging. Additional imaging examinations should be performed on the basis of first-line tests to clarify the lesions. To avoid missed lesions, more stringent criteria should be applied for determining surgical endpoints beyond the traditional Miami criteria. This case report will provide valuable clinical experience for the diagnosis and treatment of similar cases in the future.