IgA nephropathy occurring in the context of previous acute glomerulonephritis

A 37-year-old female presented with acute onset of glomerulonephritis 10 days following an upper respiratory infection. Serum complement components were depressed and proteinuria exceeded 3.0 g daily. Renal biopsy revealed granular staining of IgG and C3 along the basement membrane as well as small amounts of IgA in a linear pattern. Gradual resolution of symptoms was followed by recrudescent proteinuria 2 years later. Renal biopsy at this time revealed large deposits of IgA in a mesangial staining pattern consistent with a diagnosis of IgA nephropathy. Possible mechanisms for this unusual morphologic transformation include enhanced mesangial permeability as well as mesangial sequestration of an exogenous antigen.