Rebound thymic hyperplasia after adrenalectomy in a patient with Cushing syndrome caused by adrenocortical adenoma: A case report.

Rationale: The development of rebound thymic hyperplasia (RTH) has been reported in patients who have recovered from stressful conditions such as surgery and steroid therapy. We report a case of RTH following the resolution of hypercortisolism after adrenalectomy for the treatment of adrenocortical adenoma in a patient with Cushing syndrome.

Patient Concerns: A 5-month-old female infant with a history of overeating, hirsutism, and excessive weight gain for the previous 2 months was referred to the hospital. The laboratory results revealed elevated 24-hour urinary free cortisol levels. An overnight dexamethasone suppression test showed no response. Abdominal imaging revealed a right-sided suprarenal mass measuring 4_3cm. Histology showed an adrenocortical adenoma. Thus, she underwent a right adrenalectomy.

Diagnoses: The patient showed clinical improvement with weight loss and normal cortisol levels over the next 4 months. Six months after the operation, a chest computed tomography showed enlargement of the left thymic lobe, which was previously nonexistent.

Interventions: A fine needle aspiration biopsy was performed, and histological examination revealed diffuse thymic hyperplasia.

Outcomes: At the 1-year follow-up, the chest imaging studies showed resolution of the RTH.

Lessions: An understanding of RTH after adrenalectomy as a treatment for cortisol-producing adrenocortical tumors is important for the prevention of unnecessary surgical intervention and therapy.