MPO and vasculitis: 1. Symptoms and signs characteristic of systemic vasculitis2. At least one of the following:a.histological evidence of vasculitis and/or granuloma formationb. positive serology for ANCA (either cANCA/PR3 or pANCA/MPO)c. specific indirect evidence of vasculitis3. No other diagnosis to account for symptoms or signsAll criteria must be fulfilled