Primary Hyperparathyroidism Due to an Ectopic Parathyroid Adenoma Located in the Posterior Part of the Esophagus.

Parathyroid glands typically exist in pairs on the posterior surface of the thyroid, and primary hyperparathyroidism (PHPT) is often caused by adenomas in these locations. However, ectopic parathyroid glands may occasionally develop in unusual sites. We present a case of a 71-year-old female patient who exhibited gradual increases in both serum calcium and parathyroid hormone (PTH) levels, along with the development of osteoporosis, suggesting the presence of PHPT. Routine examination, including ultrasonography, sometimes fails to identify an ectopic parathyroid adenoma. In this case, further investigation using methoxyisobutylisonitrile (MIBI) scintigraphy and contrast-enhanced CT revealed an ectopic parathyroid adenoma located in the posterior part of the esophagus. After that, left parathyroidectomy was performed. Left parathyroid weight was 610 mg, and its size was 23 × 10 × 4 mm. Pathological examination confirmed the diagnosis of ectopic parathyroid adenoma. After the surgery, serum PTH and calcium levels were normalized. This case underscores the importance of considering ectopic parathyroid adenomas when ultrasonography fails to identify the lesion and highlights the importance of MIBI scintigraphy in such cases.