Thoughts about the classification of small vessel vasculitis

Abstract

The classification of small vessel vasculitis has markedly changed over the past 150 years. With the discovery of anti-neutrophil cytoplasmic autoantibodies (ANCA), renewed interest in the field has spawned investigations into the immunopathogenesis of small vessel vasculitis. This review will describe the historical basis of the classification of vasculitis, the current nosology based on the Chapel Hill Nomenclature for vasculitis and then both pathogenic and clinical reasons that support the use of the term "ANCA small vessel vasculitis" to describe the pauci-immune necrotizing small vessel vasculitides, including microscopic polyangiitis, Wegener's granulomatosis, the Churg-Strauss syndrome and pauci-immune necrotizing and crescentic glomerulonephritis.