Idiopathic Immune Complex Glomerulonephritis

Abstract

Immune complex glomerulonephritis (GN) is characterized by the presence of immune complexes in the glomerulus, typically detected by immunofluorescence microscopy and containing both immunoglobulin and complement components. These complexes trigger complement activation and inflammatory cell recruitment, leading to glomerular injury. By light microscopy, the histologic pattern is often that of membranoproliferative GN. A variety of diverse conditions have been associated with immune complex GN, including chronic infections, hematologic disease, and autoimmunity. The history of this condition reveals that over the past several decades, an increasing portion of disease originally thought to be “idiopathic” has had its underlying cause identified. Thus true idiopathic immune complex GN, in which no identifiable cause is found, is increasingly rare and should be considered a diagnosis of exclusion. The finding of an unexplained immune complex GN should prompt a thorough search for an associated systemic disease, especially hepatitis C infection, hematological malignancy, and collagen vascular diseases such as systemic lupus erythematosus. In the absence of an underlying cause, treatment is based on maintaining glomerular health with blood pressure control and proteinuria reduction, while aggressive cases require immune suppression to decrease immune complex formation and the subsequent inflammatory cascade.