Etiology-based diagnostic approach to proliferative glomerulonephritis.

Proliferative glomerulonephritis (GN) often is classified based on the pattern of injury. The pattern of injury does not reveal the underlying cause. New insights into the causes of proliferative GN suggest that determining the type of deposits is more likely to provide clues to the underlying cause than determining the pattern of injury. This article proposes a new classification of proliferative GN that links findings from both immunofluorescence and light microscopy. The basis of the classification is whether the proliferative GN is immune complex mediated, pauci-immune, or complement mediated; the type of immunoglobulin deposits and complement factors then determine or suggest the underlying cause. One of the aims of the proposed classification system is to focus on the pathophysiology of the GN with emphasis on the underlying cause, leading to appropriate evaluation and management. The second aim is to simplify and standardize the classification of proliferative GN.