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Diagnosis: IgG4-Related Disease

Immunoglobulin G4-related diseases (IgG4-RDs) is a clinical entity that often involves multiple organs and is characterized by high levels of serum IgG4, dense infiltration of IgG4+ cells and storiform fibrosis. Cellular immunity, particularly T-cell mediated immunity, has been implicated in the pathogenesis of IgG4-RDs. The most frequent renal manifestations of IgG4-RD are IgG4-related tubulointerstitial nephritis, membranous glomerulopathy and obstructive nephropathy secondary to urinary tract obstruction due to IgG4-related retroperitoneal fibrosis. IgG4-RD diagnosis should be based on specific histopathological findings, confirmed by tissue immunostaining, typical radiological findings and an appropriate clinical context. The first line treatment is the steroids with two warnings: Steroid resistance and relapse after discontinuation. In the case of steroid resistance, B cell depleting agents as rituximab represent the second-line treatment. In the case of relapse after discontinuation, steroid treatment may be associated with steroid sparing agents (Salvadori M, Tsalouchos A. Immunoglobulin G4-related kidney diseases: An updated review. World J Nephrol. 2018;7(1):29-40. [Full text link]).

In our case, although there was no typical storiform fibrosis, the abundance of IgG4 plasma cells, the clinical context and the confirmation of a similar involvement in the lymph nodes, with elevated serum IgG4 levels, helped us to confirm the diagnosis.

Visit the Chapter: Tubulointerstitial diseases of our Tutorial.

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