Ectopic parathyroid adenoma with severe hungry bone syndrome: a case report.

: The presentation rate of ectopic mediastinal parathyroid adenoma is about 5 approximately 22%. Ectopic parathyroid adenoma is a common etiology of failed parathyroid surgery as well as a diagnostic challenge to clinicians. We reported a case of ectopic mediastinal parathyroid adenoma. A 20-year-old girl presented with arthralgia for 2 years before hyperparathyroidism was diagnosed. Parathyroid ultrasonography failed to find the lesion, but a vivid uptake in the superior mediastinum was discovered by thallium-201 (Tl-201) and technetium-99m-sestamibi (Tc-99m-MIBI) images. Removal of the ectopic adenoma resulted in severe Hungry bone syndrome, which required a large amount of calcium and phosphorous supply. Later, the patient suffered from bilateral femoral neck fracture due to marked osteoporosis. Bone mineral density study revealed marked increase of fracture risk. Although bone disorder is rare in cases of hyperparathyroidism nowadays, it still should be considered in patients with arthritis of unknown etiology like our case. Early diagnosis and treatment can reduce the morbidity.