Churg-Strauss syndrome is a systemic and pulmonary vasculitis, defined by its association with severe asthma and with hypereosinophilia of the blood and tissues. The systemic vasculitis is a small-vessel vasculitis frequently associated with purpura, mononeuritis multiplex, and, more rarely, with rapidly progressive glomerulonephritis or diffuse alveolar hemorrhage. Its prevalence of 7 to 13 per million population makes it one of the rarest of the systemic vasculitides. Anti-MPO (antimyeloperoxidase) pANCA (ANCA with a perinuclear fluorescence pattern) is present in 35-40% of cases and appears to determine a subgroup of patients with a higher frequency of renal damage, alveolar hemorrhage, and central nervous system damage. Cardiac involvement is an important cause of morbidity and the leading cause of mortality in Churg-Strauss syndrome. Treatment is based on corticosteroid therapy and immunosuppressive drugs (cyclophosphamide and azathioprine) and is determined according to validated prognostic criteria (Five-Factor Score). Complete remission occurs in almost 90% of cases, and the 10-year survival rate has reached 79.4%. Relapses are frequent (25% of cases) and even after recovery from vasculitis, most patients (90%) still have asthma requiring corticosteroid treatment.