Overview of IgG4-related respiratory disease

Immunoglobulin G4 (IgG4)-related disease is a newly recognized systemic disease characterized by elevated serum level of IgG4, IgG4-positive plasma cell infiltration into affected lesions, and fibrosis. In 2011, the comprehensive diagnostic criteria for IgG4-related disease were proposed by the Study Group of Intractable Diseases from the Ministry of Health, Labour and Welfare, Japan (MHLW). However, since the treatment has been recently specified and classified, the Study Group of MHLW recognized the necessity of having organ-specific diagnostic criteria, focusing on the specific features of lesions in individual organs, and therefore, a subcommittee of MHLW established the diagnostic criteria for IgG4-related respiratory disease. This review aimed to describe the clinical features, laboratory findings, and diagnostic criteria for IgG4-related respiratory disease. Based on data collected and analyzed by the subcommittee of MHLW, the essence of the clinical, imaging, and pathological findings has been summarized as "diagnostic criteria for IgG4-related respiratory disease". Further evaluation is expected to validate these criteria.