7200 A Unique Case Of Hypercalcemia From Primary Hyperparathyroidism With Thymoma And Concurrent Pulmonary Tuberculosis

Abstract Disclosure: S. Jing Hang Randy: None. L. Huiling: None. Background: Several case reports have reported the rare association of thymoma with primary hyperparathyroidism. We describe a unique case of hypercalcemia with such association but was also found to have concurrent pulmonary tuberculosis. Clinical Case: A 50-year-old Indian female with a significant history of anterior mediastinal mass underwent median sternotomy with mass resection and was found to have peri-operative hypercalcemia. Her only complaint was chronic cough. Initial investigations showed high adjusted calcium 2.78 mmol/L (2.15– 2.50 mmol/L), normal phosphate 1.1 mmol/L (0.8– 1.4 mmol/L) and high PTH 24.7 pmol/L (1.6– 6.9 pmol/L). Apart from the mediastinal mass, a whole-body CT scan showed multiple prominent mediastinal lymph nodes with non-specific subcentimetre lung nodules. The post-operative finding was a Type AB thymoma with necrotizing granulomatous inflammation in adjacent station I lymph node. Differentials for patient’s hypercalcemia included primary hyperparathyroidism, malignancies such as lymphomas and infectious causes in particular tuberculosis. Her 25-OH Vitamin D was low at 9 ug/L (30 - 100 ug/L), 1,25-dihydroxyvitamin D was elevated at 205 pg/mL (18-64 pg/mL) while creatinine, ALP, serum ACE and PTHrP were unremarkable. She was subsequently admitted for worsening hypercalcemia, fever and left pleural effusion with generalized lymphadenopathy where she underwent an Endobronchial Ultrasound-guided Transbronchial Needle Aspirate of station IV lymph nodes before being started on tuberculosis treatment. The AFB culture showed Mycobacterium Tuberculosis Complex thereafter. Parathyroid sonography revealed a 2.2cm x 0.9cm x 0.8cm lobulated hypoechoic lesion posterior to the inferior pole of left thyroid lobe. However, a confirmatory sestamibi scan could only be done 6 weeks post-thymectomy given the raw surgical bed, with a possibility of false-negative result for cervical parathyroid adenoma given a recent thymectomy. It subsequently showed a hyperfunctioning left inferior parathyroid nodule with no other suspicious focal uptake in the neck or mediastinum. Patient underwent a focused left parathyroidectomy. Histology showed features consistent with parathyroid adenoma. A stepwise trajectory of her calcium normalization was observed with hydration, intravenous zoledronic acid for her osteoporosis, tuberculosis treatment, adjuvant radiation therapy for her thymoma with margins involvement, and parathyroidectomy. Conclusion: This case illustrates the challenges faced while considering localizing scans for primary hyperparathyroidism with recent thymectomy given the common embryological origin of inferior parathyroid and thymus. It also demonstrates the possible co-existence of separate pathologies in hypercalcemia and the need to exercise prudent clinical judgement to further evaluate for these various etiologies. Presentation: 6/2/2024