Definition
• Multisystem disorder characterized by the triad of asthma, peripheral blood eosinophilia, and vasculitis
Clinical features
Epidemiology
• No sex predilection
• More often affects young adults
Presentation
• Mainly involves the upper respiratory tract, lungs, skin, and peripheral nerves
• Patients usually present with allergic rhinitis, nasal polyps, asthma, peripheral eosinophilia, peripheral neuropathy, cutaneous leukocytoclastic vasculitis
• Serum p-antineutrophil cytoplasmic antibody (p-ANCA) is commonly present
• Elevated IgE is a characteristic finding
Prognosis and treatment
• Most patients respond to corticosteroids and immunosuppressants
Pathology
Histology
• Combination of eosinophilic pneumonia, asthmatic bronchitis, granulomatous inflammation (allergic granulomas), and vasculitis
• Eosinophilic pneumonia is characterized by abundant eosinophilic infiltration admixed with chronic inflammatory cells
• Allergic granuloma is usually necrotizing; characterized by a necrotic center replete with eosinophils and eosinophilic debris, with palisading epithelioid histiocytes around central necrosis
• Eosinophilic vasculitis is composed of eosinophils, chronic inflammatory cells, histiocytes, and multinucleated giant cells
• Similar morphological features seen in extrapulmonary involvement in Churg-Strauss syndrome
Immunopathology/special stains
• Not contributory
Main differential diagnoses
• Wegener granulomatosis: geographical dirty blue necrotizing granulomas and serological abnormalities (increased c-ANCA)
• Microscopic polyangiitis: vasculitis restricted to arterioles, venules, and capillaries; neutrophilic vasculitis and pulmonary hemorrhage; systemic involvement including glomerulonephritis, fever, myalgia, and arthralgia
• Hypersensitivity pneumonia: characterized by chronic inflammatory interstitial pneumonia accompanied by poorly formed granulomas with interspersed eosinophils and bronchiolitis
• Allergic bronchopulmonary fungal disease: abundant allergic mucin characterized by presence of eosinophilic mucin, eosinophils, and colonization of fungi
• Eosinophilic pneumonia secondary to infections: evidence of parasites or fungi
• Drug-induced eosinophilic pneumonia: positive history of drug use
• Idiopathic eosinophilic pneumonia: eosinophilic pneumonia with unknown causes; may be associated with mild interstitial pneumonia and eosinophilic microabscess
Fig 1 Pulmonary Churg-Strauss syndrome. Eosinophilic pneumonia and eosinophilic vasculitis with eosinophils in the alveolar spaces, vascular walls, and lumens.
Fig 2 Pulmonary Churg-Strauss syndrome. A, Eosinophilic abscess with numerous eosinophils. B, Eosinophils interspersed among granulomas.
Fig 3 Pulmonary Churg-Strauss syndrome. Eosinophilic vasculitis with eosinophils infiltrating the vascular wall; fibrinoid necrosis also present.