Pulmonary function tests findings and their diagnostic value in patients with IgG4-related disease

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition that can affect the lung and most other organs. The main features of IgG4-RD are high serum IgG4 concentrations and infiltration of IgG4-positive plasma cells into the affected organs. IgG4-RD is a protean condition that mimics many malignant, infectious, and inflammatory disorders. This condition links many disorders previously regarded as isolated, single-organ diseases without any known underlying systemic condition; for example, autoimmune pancreatitis, sclerosing cholangitis, interstitial pneumonia retroperitoneal fibrosis, and many more. These diseases were recognized as a unified entity only 10 years ago (1,2)