Inflammatory pituitary lesions

Inflammatory pituitary lesions are rare but important differential diagnoses of nonfunctioning pituitary masses. Primary hypophysitis as an autoimmune disorder has received increasing attention over the past decades. In the last decade, immune checkpoint inhibitor–induced hypophysitis has emerged as a new type of secondary hypophysitis. Various pituitary tumors may also cause secondary hypophysitis. Systemic, noninfectious granulomatous diseases that can involve the pituitary region include sarcoidosis, granulomatosis with polyangiitis, Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. Furthermore, infectious diseases can affect the pituitary gland. The differential diagnosis of these inflammatory conditions is challenging because of the similarities in clinical presentations and radiological signs. This chapter describes the essential features of the spectrum of inflammatory pituitary lesions.