A case of IgG4-related pulmonary disease with rapid improvement.

We report a 72-year-old man with respiratory involvement of immunoglobulin G4 (IgG4)-related disease, who developed dry cough and shortness of breath on effort. The chest computed tomography scan image showed massive and diffuse ground-glass opacity, interlobular thickening, and bronchial wall thickening. The infiltration of IgG4-positive plasma cells in the transbronchial lung biopsy and high serum IgG4 concentrations were found. The patient was treated with 0.6 mg/kg oral prednisolone and showed rapid improvement. This is a case of IgG4-related disease in which the only complication was respiratory involvement.