Abstract / Summary
Primary mesangial proliferative glomerulonephritis (MesPGN) refers to the light microscopic description of increased mesangial cells (greater than three cells per mesangial area) without endocapillary proliferation, necrosis, and crescents in the absence of another primary glomerulopathy (e.g., IgA nephropathy) or systemic illness (e.g., lupus). Immunofluorescence may be negative or contain mesangial IgM +/− complement (IgM nephropathy) or C1q + immunoglobulin (C1q nephropathy). The presence of either immune deposits or mesangial proliferation per se connotes a worse prognosis when compared with minimal changes. Segmental sclerosis may be present and imparts a worse prognosis regardless of mesangial proliferation or immune deposits. Primary MesPGN may present clinically as nephrotic syndrome, non-nephrotic proteinuria +/− hematuria, or isolated hematuria. If nephrotic, MesPGN may be considered nosologically as a primary podocytopathy with secondary mesangial cell activation, especially when immunofluorescence is negative. Such podocyte injury may be driven by circulating factors and/or antibodies directed against podocyte-specific antigens. Alternatively, IgM or complement deposits suggest an antibody-driven immune-complex etiology primarily affecting the mesangium with secondary podocyte injury analogous to IgA nephropathy, especially when presenting as non-nephrotic proteinuria or hematuria. No randomized controlled trials have addressed immunosuppression in primary MesPGN. If non-nephrotic or isolated hematuria, supportive care is indicated. If nephrotic, initial immunosuppression should mimic that of the primary podocytopathies (high-dose oral steroids), although tacrolimus may substitute if there is a concern for steroid toxicity. For frequently relapsing/steroid-dependent cases, rituximab is our choice for adults, probably with maintenance dosing. Steroid-resistant cases may be treated with calcineurin inhibition.