Immunoglobulin G4-associated disease in pulmonology

Abstract

A brief review and description of two clinical cases of an IgG4-related disease are presented, one with lung and salivary glands involvement, the other with lung involve- ment associated with post-COVID changes and diagnosed clinically as a neoplasm. Verification of an IgG4-associated disease, which is characterized by stereotypical clinical manifestations that make differential diagnosis difficult, became possible due to the histological and immunohistochemical study of biopsy and surgical specimen of the salivary glands and lungs. Diagnostic criteria developed by Japanese authors in 2019 were used. Literature review and own observations made it possible to assume an IgG4-associated disease affecting the lungs and salivary glands a reallife, but rarely diagnosed form of idiopathic fibrosis of various organs, primarily pneumofibrosis. In the IgG4-associated disease the main diagnostical methods with high specificity are histological and immunohistochemical ones with antibodies to CD138, IgG, IgG4, and morphometry. They allow to detect massive infiltration of tissue with lymphocytes, eosinophils, and plasma cells expressing IgG4, in combination with obliterating phlebitis.