Churg-Strauss syndrome (CSS) is a disorder characterized by asthma, peripheral eosinophilia (usually greater than 10%), and pulmonary radiographic abnormalities. Other presenting signs include peripheral neuropathy, sinus disease (granulomas, sinusitis, and polyposis), and cutaneous lesions (leukocytoclastic vascultitis, ulcerations, palpable purpura, petechiae, nodules, and papules). Organ system involvement may include the central nervous system (cerebral infarction, convulsions, coma, confusion, cranial nerve involvement, or granulomatous nodules), the heart (congestive heart failure, valvular destruction, pericarditis, pericardial effusion, and endomyocarditis), and the kidneys, (focal segmental glomerulonephritis characterized by hematuria and/or proteinuria). Gastrointestinal involvement (eosinophilic gastroenteritis, mesenteric vasculitis, and colonic vasculitis) is associated with a poor prognosis. Asthma generally precedes other symptoms. Associated pulmonary abnormalities include transient patchy alveolar opacities, diffuse interstitial infiltrates, nodular densities, and an eosinophil-rich pleural effusion. Alveolar hemorrhage occurs infrequently. The differential for eosinophilic lung disease includes Churg-Strauss syndrome, acute eosinophilic pneumonia, chronic eosinophilic pneumonia, idiopathic hypereosinophilic syndrome, asthma, allergic bronchopulmonary aspergillosis, parasitic infections during their pulmonary phase, and medication reactions.

An elevated IgE level is appreciated along with the above-mentioned eosinophilia. A portion of cases are p-ANCA (MPO-ANCA) positive. ANCA testing should be performed before initiating steroid therapy as the sensitivity increases with active, untreated disease. Increasing eosinophilia and IgE levels indicate disease flares. Histopathologic examination of granulomatous lesions may aid in establishing the diagnosis.

Many different criteria systems exist, however the diagnosis is often missed using these criteria; therefore, this remains a clinical diagnosis. The Five Factor Score (FFS) may be used to estimate prognosis and includes: an elevated creatinine greater than 1.58 mg/dL, proteinuria greater than 1 gm/day, sever gastrointestinal involvement, cardiomyopathy, and CNS involvement. A lack of factors portends a better prognosis whereas the presence of three or more factors is associated with a poor prognosis.

Therapy varies depending on the disease severity. Relapses are common and patients require lifelong follow-up for flares. Therapy may be initiated with steroids with or without cyclophosphamide. Refractory cases may require treatment with interferon alpha, rituximab, or omalizumab. Consultation with a specialist in vasculitic care (rheumatologist, pulmonologist, or nephrologist) is prudent.