Finding The Glands: A Case of Atypical Parathyroid Anatomy

Primary hyperparathyroidism results from autonomous parathyroid hormone production from one or more parathyroid glands and definitive treatment is surgical resection. The anatomy of the parathyroid glands can be highly variable between patients. We present the case of a patient with primary hyperparathyroidism and atypical parathyroid anatomy.

Case Description :

Patient is a 53-year-old female with past medical history or primary hypothyroidism, obesity (status post bariatric surgery), and vitamin D deficiency who was incidentally noted to have hypercalcemia. Her initial calcium level was 10.7 mg/dL with a parathyroid hormone (PTH) of 55 pg/mL. Subsequent evaluation showed osteoporosis and hypercalciuria so decision was made to pursue parathyroidectomy.

During surgery, she underwent left inferior parathyroidectomy and biopsy of the right superior and inferior parathyroids. These glands had grossly normal size and color but pathology showed that all three were hypercellular. The left superior parathyroid gland was not localized and there was no intraoperative drop in her PTH level despite undergoing left central neck dissection and left hemithyroidectomy. She had persistent primary hyperparathyroidism post-operatively.

She underwent Sestamibi scan which showed focus of ectopic uptake in the right superior mediastinum. She underwent PTH venous sampling to confirm this ectopic location but results were inconclusive. The patient had repeat surgery and was found to have a right mediastinal parathyroid gland with 100% cellularity in addition to the previously identified left inferior, right superior, and right inferior parathyroid glands. After surgery, her calcium and parathyroid levels have normalized.

Discussion :

This case highlights an unusual variant for parathyroid anatomy. Classically, four parathyroid glands are located within the central neck; two glands bilaterally, located posterior to the thyroid gland, and designated as superior or inferior based on their location related to the recurrent laryngeal nerve. There can be variation in both number and location of the glands with the most common location of ectopic glands being within other places in the neck or the superior mediastinum.  Embryologically, the glands are derived from endoderm of the third and fourth pharyngeal pouches that migrates with more variability in the inferior glands’ locations. This case had an atypical, asymmetric distribution of glands with three on the right and only one gland on the left side. It also demonstrates the different techniques available for the localization of autonomous parathyroid glands and the difficulty of surgical planning with ectopic glands.