Immunodeficiency, GM4 Deficiency Syndrome, and Hypogammaglobulinemia
GM4 deficiency syndrome is often mistakenly used to refer to IgG4-related disease (IgG4-RD). IgG4-related disease is not a classical immune deficiency. Instead, it is a systemic immune-mediated inflammatory disorder characterized by dysregulation of the immune system and increased production of the antibody subclass IgG4. This condition can involve multiple organs and lead to chronic inflammation and fibrosis. Key Features IgG4 Antibodies IgG4 is a subclass of immunoglobulin G (IgG), which is part of the antibody system used by the immune system to recognize and neutralize pathogens. In IgG4-related disease, serum IgG4 levels are often elevated. Increased IgG4-producing plasma cells infiltrate tissues and contribute to inflammation and organ dysfunction. Fibrosis A major pathological feature of IgG4-related disease is fibrosis. This refers to excessive formation of connective tissue that replaces normal tissue. Fibrosis can cause organs to become enlarged, stiff, and less funct...