IgG4-related disease is a recently-described disease. It involves multiple organs including pancreas, salivary glands, kidneys, lungs, lymph nodes in which a characteristic histological change is identified. A dense lymphoplasmacytic infiltration with "storiform" fibrosis is replacing the normal organ parenchyma, frequently with a mass-like appearance observed radiologically. The plasma cells containing predominantly IgG4, a subclass of IgG, are the hallmark of the disease.
Although IgG4 is present in both serum and tissue of affected organs, its role in pathogenesis of the disease is still unclear and required further research. IgG4-related disease is accepted to be an autoimmune disease.
The main lesion of kidneys is tubulointerstitial nephritis (TIN). The histopathology is similar to those found in other organs which is lymphoplasmacytic infiltrate and "storiform" fibrosis involving tubulointerstitial compartment. Many eosinophils can be seen as in drug-induced TIN. Immunofluorescence reveals tubular basement membrane (TBM) immune complex deposits with staining of IgG, kappa and lambda light chains. Immunohistochemical staining of IgG4 is required to demonstrate IgG4+ plasma cells, generally with >10 cells/high power field (hpf). A minority may presents with membranous nephropathy.
IgG4-related disease
IgG4-related kidney disease
