Mepolizumab As a Steroid-sparing Treatment Option in the Churg Strauss Syndrome

Specific Aims: 1. Document the safety of mepolizumab therapy in patients with CSS. 2. Demonstrate the steroid sparing effect of mepolizumab therapy by decreasing corticosteroid dosage while using this anti-IL5 therapy. 3. Demonstrate the efficacy of anti-IL5 therapy in improving the signs and symptoms of CSS by: 1. Measuring serum markers of CSS disease activity, including: peripheral eosinophilia, erythrocyte sedimentation rate, anti- neutrophil cytoplasmic antigen, C-reactive protein and IgE levels. 2. Assessing the activity level of vasculitis via the Birmingham Vasculitis Activity Score 3. Evaluating asthmatic response via serial peak flow and FEV1 measurements as well as asthma symptom scores using the Juniper scale. 4. Assessing changes in novel parameters such as fractional excretion of nitric oxide and IL-5 levels.