IgG4-related hypophysitis presenting as a pituitary adenoma with systemic disease

Summary Hypophysitis is a rare inflammatory disorder that can mimic a pituitary tumor clinically or radiologically. Furthermore, immunoglobulin G4 (IgG4)-related systemic disease is only a just recently characterized disorder. It can manifest as a systemic disease involving multiple organs, including the pancreas, salivary glands, lungs, liver, bile duct, gallbladder, kidneys, and retroperitoneum. It is characterized by a high serum level of IgG4 clinically and dense lymphoplasmacytic infiltration with sclerosis and phlebitis histologically. Herein, we report the case of a man 66 years of age who presented with nausea, vomiting, and poor appetite with a body weight loss of 4 kg. Image study revealed a pituitary infundibulum mass, right-posterior mediastinal and paraspinal masses, as well as infiltrating masses in bilateral kidneys. Therefore, he received a thoracoscopic biopsy for the right-posterior mediastinal and paraspinal masses and a pathologic examination reported an IgG4-related inflammatory pseudotumor. Then, transsphenoidal removal of the infundibulum mass was performed. Histologically, the infundibulum mass represented a IgG4-related hypophysitis manifested as an infiltration of plasma cells, lymphocytes, histiocytes, and some eosinophils with a fair number of IgG4-immunoreactive plasma cells. After the operation was complete, the patient took 5 mg of prednisolone every 2 days for 3 months. A follow-up computed tomography scan revealed improvement of the infiltrating masses in the bilateral kidneys.