Granulomatosis with polyangiitis and microscopic polyangiitis: common features and differences

Patients with ANCA-associated vasculitides usually present with similar clinical manifestations (fever, joint pain, lung and kidney diseases, purpura, etc.). However, signs of granulomatosis inflammation of the upper and lower respiratory tract and/or orbit allow to differentiate granulomatosis with polyangiitis (GPA) from microscopic polyangiitis (MPA). Circulating ANCAs are the key laboratory sign of ANCA-associated vasculitis, although they can be negative in a proportion of patients and can be found in patients with other diseases. GPA is usually associated with ANCAs againts proteinase-3, whereas ANCAs against myeloperoxidase are more common in patients with MPA. The authors present two patients with ANCA-associated vasculitides and discuss the common clinical features and differences between GPA and MPA and new classification criteria.