[A case of possible immunoglobulin G4-related disease (IgG4-RD) with retroperitoneal fibrosis and central diabetes insipidus due to infundibulohypophysitis].

We report a case of possible immunoglobulin G4-related disease(IgG4-RD)that resulted in complications such as retroperitoneal fibrosis and infundibulohypophysitis. The patient was a 72-year-old male who presented with polyuria and polydipsia. Magnetic resonance imaging(MRI)revealed a thickened pituitary stalk and contrast enhancement with gadolinium. T1-weighted imaging revealed that the posterior pituitary high-signal zone had disappeared. Central diabetes insipidus was diagnosed on the basis of results of the hypertonic saline test. In addition, pressure due to retroperitoneal fibrosis resulted in hydronephrosis and elevated serum IgG4 levels. Because it was determined that the patient could have IgG4-RD, he was administered prednisolone, following which a decrease in the size of the pituitary stalk and retroperitoneal fibrosis was observed. IgG4-RD is characterized by elevated serum IgG4 levels and the infiltration of IgG4-positive plasma cells into various organs, including the central nervous system. Recently, IgG4-RD research teams organized by the Ministry of Health, Labour and Welfare established guidelines for the diagnosis of IgG4-RD. According to these guidelines, this case would fall under the category of "possible IgG4-RD." This case suggested that when infundibulohypophysitis is detected by neuroradiology, further investigation into the possibility of IgG4-RD should be recommended.