Early recurrence of primary hyperparathyroidism due to an ectopic parathyroid gland
M Moriarty, P Machenahalli, C Lim, J Todd, Hammersmith Hospital.
We present the case of a 41 year old gentleman with early recurrence of primary hyperparathyroidism due to an ectopic parathyroid gland.
This gentleman with a background of MEN1 mosaic was diagnosed with primary hyperparathyroidism. Localisation studies showed large lesion in region of left inferior parathyroid gland on sestamibi (MIBI) scan and right parathyroid adenoma on ultrasound. Given his genetic diagnosis he underwent subtotal parathyroidectomy in 2013. He had four gland hyperplasia at time of surgery which is typical of MEN patients. Post-operative PTH was 3.4, consistent with residual parathyroid tissue.
At the time of surgery he had an incidental finding of a lymph node which was positive for papillary thyroid carcinoma (PTC). Following standard treatment for PTC with thyroidectomy and radioiodine ablation he remained under surveillance.
18 months post operatively he developed hypercalcemia. Biochemistry at that time was consistent with recurrent primary hyperparathyroidism. Further imaging showed no evidence of recurrent parathyroid adenoma on ultrasound however MIBI showed a focus of activity in the anterior mediastinum consistent with ectopic parathyroid gland. Stimulated thyroglobulin was negative reducing the likelihood of recurrent PTC.
Ectopic parathyroid glands can be seen in up to 15% of patients with primary hyperthyroidism. Often they are detected on pre-operative localisation studies allowing for more targeted operative approach. This case is unusual as he had a positive MIBI scan preoperatively which did not demonstrate uptake within the ectopic gland. It is likely this is due to suppression from the dominant gland in the neck. Metastatic thyroid carcinoma may cause false positive on MIBI and so recurrent disease should be considered.
This case highlights the importance of on-going biochemical surveillance in primary hyperparathyroidism and the requirement for repeat imaging to guide approach to further surgical intervention.