IgG4-related kidney diseases

Immunoglobulin G4-related disease (IgG4-RD) is a systemic inflammatory disease characterized by chronic activation of the immune system with subsequent tissue fibrosis. It can affect a wide variety of different organ systems. The most common form of renal involvement (IgG4-RKD) is tubulointerstitial nephritis (TIN) with characteristic infiltrates of IgG4-positive plasma cells in the interstices and storiform fibrosis. Rarer forms with glomerular involvement and urinary obstruction caused by retroperitoneal fibrosis can also occur. The clinical presentation of IgG4-RKD is usually unspecific with only impaired kidney function and an unremarkable urinalysis. An elevated serum IgG4 level can strengthen the suspected diagnosis of IgG4-RKD. Cross-sectional imaging often demonstrates characteristic lesions close to the renal cortex, which are difficult to differentiate from malignancies. Although a rapid clinical response of IgG4-RKD to treatment with glucocorticoids is characteristic, there is often only a partial improvement in kidney function. Recurrences are frequent and the optimal management of follow-up and long-term treatment is still unclear. This article explains the various forms of IgG4-RKD in more detail.