Churg-Strauss syndrome occurring during omalizumab treatment.

To the Editor, The Churg-Strauss syndrome (CSS) is a rare type of primary vasculitis that involves smalland medium-sized blood vessels (1). The diagnosis of CSS is based on the American College of Rheumatology (ACR) criteria, which includes asthma, eosinophilia >10%, paranasal sinusitis, pulmonary infiltration, histological proof of vasculitis, and monoor polyneuropathy (2). Fulfillment of four out of these six criteria is adequate for a positive diagnosis. The clinical course of CSS includes three consecutive phases comprising a prodromal phase characterized by respiratory symptoms (rhinosinusitis and asthma), a second phase where peripheral blood eosinophilia and eosinophilic tissue infiltrates are observed, and a third phase characterized by systemic vascular manifestations (3). Fever is a symptom generally observed in all the patients, although it can be very irregular, ranging from temperatures below 39°C or even 38°C in the majority of the patients to 40°C in rare cases. The fever generally subsides some time before death (1). CSS is a rare disease and its prevalence is 13/1,000,000 in the general population (4). Omalizumab is a humanized monoclonal antibody against IgE that is effectively used to treat persistent severe asthma. Omalizumab significantly decreases asthma exacerbation rates in patients with severe persistent asthma (5).