MPO-ANCA vasculitis is morefrequently identified in patients from Japan compared to the United Kingdom, as wellas in Chinese and Southern European populations.6 Patients with PR3-ANCA are more likely to have a diagnosis of GPA (65% of GPApatients have a positive anti PR3 antibody), whereas those with the MPO-ANCAantibody tend towards features of MPA (55% of MPA patients).7 The gene discussed is MPO; the disease is microscopic polyangiitis.