IgG4 related disease (IgG4-RD) is an infiltrating and tumor-forming, inflammatory disorder. At present many aspects of its etiology and pathogenesis are unclear, although a recent survey implicated organic solvents in its etiology. The disease can affect many organs. This often includes bile ducts and/or pancreas, but may present itself in many other organs, e.g. the urinary tract, retroperitoneum, testes, lymphatic system, lung, joint, aorta, thyroid and salivary glands. Its presentation as a tumor-forming process in different organs may easily lead to misidentification as a malignancy, e.g. a cholangiocarcinoma or a lymphoma.
In this context, clinically the diagnosis is important but may be difficult. It is largely based on the pattern of organ involvement, typical histology, findings in imaging, an elevated serum IgG4, and a good response to corticosteroid therapy. However, serum IgG4 may be normal, the clinical presentation atypical and the therapy response poor. Recently, a novel technology, performing IgG4 clonality analysis of B-cell receptor repertoires in peripheral blood samples, was shown to readily and sensitively identify patients with IgG4-RD.
First line of treatment is often prednisolone, which is usually very effective in the initial phase. Relapses occur often after tapering, and in many cases low-dose corticosteroids are indicated. In therapy resistant cases anti-CD20 therapy has been used with success.
Disclosure of Interest None declared