ODP075 A Rare Case of Intrathymic Parathyroid Adenoma

: BACKGROUND: Parathyroid adenomas are the main cause of primary hyperparathyroidism (PHPT). PHPT most often affects adults between ages 50-60 and is considered rare in children and adolescents, representing less than 5% of cases1. It is more common among females than among males in the proportion 3 to 1. During embryogenesis, both the superior and inferior parathyroid glands detach from their pharyngeal origin and migrate towards their final location, posteriorly to the thyroid gland. Migration can be faulty and ectopic glands can appear along the path of embryologic descent2. We present a case of an adolescent male who presented with symptomatic PHPT in the setting of an intrathymic parathyroid adenoma. CASE PRESENTATION: 17-year-old male with no significant past medical history developed symptoms of anxiety, nausea and fatigue. Laboratory values revealed calcium 14.3 mg/dL (8.6-10.3), PTH 227 pg/mL (15-65), 25-dihydroxyvitamin D (vit-D) 8.31 ng/mL (30-100), and phosphorus 1.5 mg/dL (2.5-5. 0). He denied any personal history of bone fractures or nephrolithiasis. CT parathyroid scan showed an enhancing oblong 1.7×0.6 cm lesion in the left upper mediastinal space suggestive of a parathyroid adenoma. Focal sestamibi uptake confirmed a 1.7×0.6 cm enhancing nodule in the left upper anterior mediastinum within the thymus. He was instructed to take 2,000 IU of vit-D daily. Repeat blood work one month later showed that his serum calcium decreased to 13.4 mg/dL and PTH decreased to 122 pg/mL. Additional labs revealed vit-D 16.81 ng/mL, 1,25-dihydroxyvitamin D (calcitriol) 160 pg/mL (19.9-79.3) and 24-hour urine calcium excretion of 409 mg (0-320). Patient underwent successful excision of an intrathymic hyperplastic parathyroid gland adenoma with a >50% drop in peak PTH levels intraoperatively at 10 minutes post excision, later confirmed by pathology. CONCLUSION: This case highlights an adolescent with symptomatic primary hyperparathyroidism due to an intrathymic parathyroid adenoma. Ectopic adenomas have been reported in approximately 4 to 16% of patients with hyperparathyroidism2. When embryological development of the parathyroid glands is defective, it can predispose to the formation of ectopic glands, which is an important cause of failed parathyroid exploration. Unfortunately, PHPT has greater morbidity in the younger age group since most of these patients develop complications from the hypercalcemia, such as kidney stones, hypercalciuria, bone disease and symptoms of abdominal pain/vomiting. This case emphasizes the importance for clinicians to be aware of ectopic parathyroid adenoma in adolescents who present with symptoms and labs consistent with primary hyperparathyroidism. REFERENCES: 1. Roizen J, Levine MA. Primary hyperparathyroidism in children and adolescents. J Chin Med Assoc. 2012;75(9): 425-434. doi: 10.1016/j. jcma.2012. 06. 0122. Chang, B. A., Sharma, A. & Anderson, D. W. Ectopic parathyroid adenoma in the soft palate: a case report. J of Otolaryngol - Head & Neck Surg 45, 53 (2016). doi.org/10.1186/s40463-016-0165-z Presentation: No date and time listed