A case of IgG4-related multifocal fibrosclerosis complicated by central diabetes insipidus.

A 55-years-old man was admitted to our hospital with a 6-month history of general fatigue, purulent nasal discharge, polyuria, and polydipsia. Endocrinological findings revealed central diabetes insipidus (CDI) with mild anterior pituitary dysfunction. Imaging studies revealed thickening of the proximal end of the pituitary stalk just below the third ventricle, a mass in the paranasal sinus, and a mass encompassing the abdominal aorta. Histopathology of the mass in the paranasal sinus revealed abundant IgG4-positive plasma cells, and the IgG4 serum level was markedly elevated. Thus, he was diagnosed with IgG4-related multifocal fibrosclerosis. Therapy with prednisolone resulted in complete resolution of clinical symptoms and reduction in size of the masses in the affected organs. However, CDI remained unchanged. This is the first case in which the cause of CDI was IgG4-related multifocal fibrosclerosis. IgG4-related sclerosing disease should be included in the differential diagnosis of thickening of the pituitary stalk with CDI, and a search for extra-pituitary involvement is essential.