Primary Hyperparathyroidism: fifth parathyroid intrathymic in a young patient.

Abstract The clinical case described in this paper deals with a young female patient affected by primary hyperparathyroidism caused by an ectopic parathyroid adenoma due to a supernumerary intrathymic parathyroid. Hypercalcaemia, in association with increased levels of parathormone, was detected in the young female patient, who was, however, asymptomatic. Genetics tests for mutation of the MEN1, HRPT2 and CaSR genes were negative. She, therefore, underwent laboratory and instrument exams (ecography of the neck, scintigraphy with 201Thallium and 99mTc-Sestamibi, SPECT of the cervicothoracic region, CT of the mediastinum and thorax, nuclear magnetic resonance of the neck and thorax), without localization results in the neck. Only an intrathymic nodule was visualized. Therefore, a surgical exploration with a stomatomic approach and differed median partial sternotomy was performed. The exploration of the neck revealed four parathyroids in a typical site, which proved on the examination to be normal, except for the right superior one, which appeared to be globose and of an increased consistency. Its biopsy highlighted a limited parathyroid hyperplasia at a further histological examination. The complete surgical ablation of the thymus was conducted and it highlighted a nodule which, at the histological examination, turned out to be an adenoma of a fifth parathyroid gland. After a revision of the literature on this subject, the existence of a fifth hyperfunctioning intrathoracic parathyroid appears to be a rare occurrence as the cause of primary juvenile sporadic hyperparathyroidism. Consequently, presenting this peculiar clinical case could be of interest in similar cases evaluated by other surgeons.