Churg-Strauss syndrome

Churg-Strauss syndrome (CSS), alternatively known as eosinophilic granulomatosis with polyangiitis (EGPA), was first described in 1951 by Churg and Strauss as a rare disease characterized by disseminated necrotizing vasculitis with extravascular granulomas occurring exclusively among patients with asthma and tissue eosinophilia. EGPA is classified as a small-vessel vasculitis associated with antineutrophil cytoplasmic antibodies (ANCAs) and the hypereosinophilic syndromes (HESs) in which vessel inflammation and eosinophilic proliferation are thought to contribute to organ damage. Although still considered an idiopathic condition, EGPA is classically considered a Th2-mediated disease. Emerging clinical observations provide compelling evidence that ANCAs are primarily and directly involved in the pathogenesis of AASVs, although recent evidence implicates B cells and the humoral response as further contributors to EGPA pathogenesis. EGPA has traditionally been described as evolving through a prodromic phase characterized by asthma and rhino-sinusitis, an eosinophilic phase marked by peripheral eosinophilia and organ involvement, and a vasculitic phase with clinical manifestations due to small-vessel vasculitis. The American College of Rheumatology defined the classification criteria to distinguish the different types of vasculitides and identified six criteria for EGPA. When four or more of these criteria are met, vasculitis can be classified as EGPA. The French Vasculitis Study Group has identified five prognostic factors that make up the so-called five-factor score (FFS). Patients without poor prognosis factors (FFS=0) have better survival rates than patients with poor prognosis factors (FFS≥1). The treatment of patients with CSS must be tailored to individual patients according to the presence of poor prognostic factors. A combination of high-dose corticosteroids and cyclophosphamide is still the gold standard for the treatment of severe cases, but the use of biological agents such as rituximab or mepolizumab seems to be a promising therapeutic alternative.