Immunoglobulin G4-Related Disease: An Update

I mmunoglobulin G4-related disease (IgG4-RD) is a group of immune-mediated diseases with common clinical, serological, and pathological features. 1This group is gaining increasing recognition in the field of medicine.Common features of IgG-RD include multiple organ involvements (which have swellings resembling tumors), fibrosis, tissue infiltrates (which are positive for IgG4 positive plasma cells), and a classical pathological form of storiform lesions.][4] IgG4-RD often has multiple organ involvements.Classical manifestations include: ■ Autoimmune pancreatitis (AIP) type 1. ■ Involvement of the major salivary glands.The common lesions being enlargement or inflammation (sclerosing sialadenitis-formerly termed Mikulicz disease and Küttner's tumor).■ Proptosis, which occurs mainly due to the involvement of the orbital or lacrimal gland.Orbital pseudotumor is an important differentiating pathology.■ Retroperitoneal fibrosis, frequently occurring as chronic periaortitis.Three classical features of IgG4-RD include swellings or masses that resemble or have a predilection to form tumors, an IgG4 rich collection of plasma cells in the inflammatory infiltrate and elevated serum IgG4 levels.Such swellings or masses can press on nerves or blood vessels producing focal vascular and or neurological deficits.Common clinical conditions associated with IgG4-RD include dacryoadenitis, myositis, inflammatory orbital disorders, orbital pseudotumor, hypophysitis, meningitis, and the involvement of one or more cranial nerves. 1 Other systemic and ocular disorders that resemble IgG4-RD include inflammatory diseases and vasculitis such as sarcoidosis, granulomatosis with polyangiitis, giant cell arteritis, Behcet's disease, thyroid eye disease, inflammatory histiocytosis, or rheumatoid arthritis; neoplastic diseases such as lymphoma, inflammatory myofibroblastic tumor, neoplastic histiocytosis, meningioma, or metastasis; and infectious diseases such as tuberculosis.Also included are conditions in the inflammatory pseudotumor category, which are currently considered idiopathic.The exact incidence of IgG4-RD is unknown.Wallace et al, 2 retrospectively examined 14 cases of pachymeningitis at their institution over 25 years and found that IgG4-RD accounted for four of those cases or 66% of previously labeled idiopathic cases.Therefore, cases previously labeled as idiopathic