Table 1.

Classification of vasculitis according to extent and severity at presentation

Disease Subgroup	Definition	ANCA Serology
Localized	Vasculitis confined to one organ system, no systemic disturbance	Often negative
Early systemic	Vasculitis in at least one organ system with systemic features without threatened vital organ function	Usually positive
Generalized	Vasculitis in at least one organ system with systemic features and threatened vital organ function	Usually positive
Severe	Vasculitis in at least one organ system with systemic features and vital organ function failure (SCr ≥500 μmol/L [≥5.7 mg/dl] if kidney involvement)	Usually positive
Refractory	Failure of standard induction regimen	Positive or negative

SCr, serum creatinine.