Case Report: An undescended intravagal parathyroid adenoma: a rare cause of refractory primary hyperparathyroidism and severe osteoporosis.

Ectopic intravagal parathyroid adenomas represent an exceedingly rare clinical entity. Embryologically, parathyroid glands develop from the third and fourth pharyngeal pouches, migrating to their definitive locations on the inferior and superior aspects of the thyroid. While ectopic locations are well described, intravagal variants are rare, with few documented cases in the literature. We report an additional unique case of a patient with persistent hypercalcemia and severe osteoporosis following a failed bilateral neck exploration for primary hyperparathyroidism. Following multimodal structural and functional radiological evaluation, an ectopically undescended parathyroid adenoma was identified and subsequently confirmed intraoperatively to be situated intravagal.