Nomenclature and classification of vasculitis: lessons learned from granulomatosis with polyangiitis (Wegener's granulomatosis).

Names influence how something is perceived. Diagnostic terms (diagnoses) are the names of diseases that are usually derived either from some distinctive characteristic of the disease or include an eponym recognizing someone who elucidated the disease. No matter how logical and appropriate a name may be, if it is not usable and used it is of no lasting value. This brief commentary focuses on the nomenclature of systemic vasculitides, and uses as a prime example Wegener's granulomatosis, which has been renamed recently 'granulomatosis with polyangiitis', in part because of concerns about the suitability of Friedrich Wegener as the source of an eponym. The most distinctive pathological feature of Wegener's granulomatosis is multi-focal necrotizing inflammation that has long been called granulomatosis. The systemic variant of Wegener's granulomatosis also is characterized by inflammation in many different vessels or different types, i.e. polyangiitis. Thus, granulomatosis with polyangiitis is a very appropriate alternative term for Wegener's granulomatosis. This term also is in accord with the name for a closely related vasculitis, i.e. microscopic polyangiitis. Terms that indicate aetiology and pathogenesis, when known, are useful to include in names for diseases (diagnoses). Anti-neutrophil cytoplasmic autoantibodies specific for myeloperoxidase (MPO-ANCA) or proteinase 3 (PR3-ANCA) are implicated in the cause of granulomatosis with polyangiitis and thus also should be specified in the diagnosis (e.g. PR3-ANCA-positive granulomatosis with polyangiitis or MPO-ANCA-positive microscopic polyangiitis). As our understanding of the clinical manifestations, pathogenesis and aetiology of vasculitides change over time, the names and approaches for diagnosing these diseases will change accordingly.