Rewriting the histological classification of lupus nephritis.

The World Health Organization (WHO) classification of lupus (SLE) nephritis was published almost 20 years ago, and there is world-wide recognition of its utility in the diagnosis and treatment of SLE glomerulonephritis (GN). However, a number of problems have been recognized: The classification of severe segmental (WHO class III > or = 50%) and membranous glomerulonephritis (MGN) complicated by the lesions of severe segmental or diffuse GN (WHO classes Vc > or = 50% or Vd) is ambiguous; The implications of non-immune complex pathogenic mechanisms are not acknowledged and SLE interstitial nephritis and vasculitis are not included in the current classification. We propose a revision that retains the classes of the current WHO classification. Informed by investigations utilizing the WHO classification, it places severe segmental GN in class III (segmental GN) and mixed MGN and segmental and diffuse GN in class V (MGN). It optimizes the use of electron and fluorescence microscopy in defining controversial and ambiguous lesions. It develops subclasses based upon pathogenic insights gained since the advent of the WHO classification. Finally, it recognizes the need to include the disease specific lesions of SLE tubulointerstial nephritis and vasculitis.