Persistent Primary Hyperparathyroidism Secondary to Unusual Location of an Ectopic Parathyroid Adenoma

Persistent hyperparathyroidism (PHPT) is diagnosed by persistent hypercalcemia in the 6 months following primary parathyroidectomy. With a success rate of roughly 95%, failure of initial surgical exploration points to the possibility of an ectopic gland. High cervical parathyroid adenomas, known as undescended adenomas, occur with a frequency of less than 0.1% and account for 7% of failed parathyroidectomies.

Case Description:

A 33-year-old female presented with anxiety, panic attacks, fatigue, insomnia, joint pain, constipation, palpitations, polyuria and polydipsia. She had previous history of COVID-19, hyperlipidemia, vitamin D deficiency, and prediabetes. Vital signs were stable. Her physical exam was unremarkable with no thyromegaly, thyroid nodules or palpable neck masses. Initial labs were significant for elevated serum calcium (SCa) at 11.9 mg/dl, 24-hour urine calcium at 318 mg/24 hr and parathyroid hormone (PTH) at 284 pg/ml. All indicative of primary hyperparathyroidism.

Preoperative SPECT-CT and ultrasound showed an enlarged right-sided nodule inferior to the thyroid gland. During the initial parathyroidectomy, the suspicious nodule was resected along with three presumed parathyroid glands and cervical lymph nodes. Intraoperative PTH was 234 and 1001 pg/ml. Pathology indicated bilateral benign inferior parathyroids, benign thyroid tissue, and fibroadipose tissue. The patient continued to have persistently elevated SCa at 11.1 mg/dl. Repeat parathyroid scintigraphy was equivocal to the initial scan. A second cervical exploration with right thyroid lobectomy and carotid sheath exploration failed to treat the persistent hypercalcemia. CT neck with contrast performed shortly after second exploration demonstrated an active lymph node versus undescended parathyroid gland inferior to the right submandibular gland. During a follow up appointment, a fine needle aspiration showed parathyroid tissue. After this intervention, the SCa returned to a normal level of 9.1mg/dl and patient’s symptoms resolved. Interestingly, the submandibular adenoma biopsy led to resolution of PTH secretion. This adenoma was eventually removed surgically and pathology confirmed necrosis, likely secondary to the biopsy.

Discussion:

Ectopic parathyroid adenomas above the carotid bifurcation are a rare cause of PHPT. This case is both unique due to the etiology and resolution of this patient’s PHPT. Recent literature focuses on the multimodal imaging approach to identify cervical ectopic adenomas; however, this case illustrates there may be a role for biopsy in both the diagnosis and potential treatment of submandibular parathyroid adenomas.