Thymic Hyperplasia Developing After Treatment of Cushing’s Syndrome, Management and Literature Review

Thymic Hyperplasia Developing After Treatment of Cushing’s Syndrome, Management and Literature Review Introduction/ Background: Rebound thymic hyperplasia (RTH) has been described after the resolution of hypercortisolism from multiple conditions. It can potentially lead to a variety of diagnostic dilemmas. We describe a case where thymic enlargement was seen after unilateral adrenalectomy for adrenal Cushing’s syndrome. Thymic hyperplasia developing after treatment of adrenal Cushing’s syndrome has been very rarely reported. Clinical Case: 43 year old female with type 2 diabetes, hypertension, morbid obesity, depression underwent left adrenalectomy for management of Cushing’s syndrome. Two years after adenoma resection, the patient underwent a CT angiogram of the chest as part of a work up for chest pain which revealed a new anterior mediastinal soft tissue attenuation mass (30–40 Hounsfield units) measuring 6.5cm x2.5cm x 3.7cm. It was found to be abutting the inferior margin of the left brachiocephalic vein and anterior margin of the aortic arch. MRI chest demonstarated mild homogeneous postcontrast enhancement and loss of signal on the opposed phase T1 sequence indicating microscopic fat, deemed to be consistent with thymic hyperplasia. Patient had a detailed discussion of risks versus benefits of biopsy/surgery/conservative management with thoracic surgeon and opted to be managed conservatively. MRI Chest done at 3 month follow up showed a decrease in the size of the mass to 5.8 x 2.4 x 5.cm. She has been on chronic hydrocortisone therapy since adrenalectomy and multiple attempts to wean her off of steroids have been unsuccessful. She continues to be followed closely in the outpatient setting for presumed RTH. Clinical Lesson/ Conclusion: This case highlights the importance of recognizing RTH in patients treated for Cushing’s syndrome. Rapid enlargement of the thymus post adrenalectomy can often lead to unnecessary biopsies and surgeries. The underlying mechanism though unclear has been attributed to depletion of thymic lymphocytes caused by high cortisol concentrations of the plasma leading to RTH when the cortisol level declines. Keywords: Thymic Hypertrophy, Cushing’s syndrome, Thymic hyperplasia