IgG4-Related Disease coexisting with Behçet's Disease.

We describe a case of Immunoglobulin G4-related disease (IgG4-RD) coexisting with Behçet's disease. A 49-year-old man, with a diagnosis of Behçet's Disease for 15 years who was found to have an acute kidney injury. His investigations revealed an elevated IgG4 level and the abdominal computerized tomography showed a retroperitoneal mass, which was diagnosed to be IgG4-RD based on histology. The patient showed symptomatic and radiological improvement after starting high dose steroid for 1 month followed by a maintenance dose. Our case report suggested that the two diseases arose separately.