Hypophysitis and Granulomatous Pituitary Lesions in Systemic Diseases

In clinical practice, expansive sellar lesions are largely represented by primary diseases of the pituitary gland, mostly pituitary tumors, which can be managed by endocrinologists and/or multidisciplinary pituitary teams. Hypophysitis has long been considered as a rare disease, and is classified on the basis of pathological findings, and as primary or secondary. Nowadays, an enlarging spectrum of pituitary and/or hypothalamic inflammatory, granulomatous, or even neoplastic disorders can be recognized, which may be part of systemic conditions and require appropriate multidisciplinary management involving a variety of specialists. For example, hypophysitis is being increasingly recognized in the setting of systemic IgG4-related disorders or as side effects of immune checkpoints inhibitors in oncological patients. Lymphocytic hypophysitis may sometimes be part of autoimmune polyendocrine syndromes. Significant knowledge has been added in the last decade in the pathogenesis and management of histiocytic disorders, which may infiltrate the pituitary and/or the hypothalamus Infective causes of pituitary inflammation should not be underestimated and are increasingly recognized in immunocompromised patients. Based on updated literature on these topics, this chapter aims to place pituitary inflammatory, granulomatous, and histiocytic disorders in their systemic context and stimulate multidisciplinary collaboration in order to optimize their diagnosis and clinical management.