Pulmonary eosinophilia associated to treatment with natalizumab

Natalizumab (Tysabri(®)) is a leukocytes chemotaxis inhibitor that decreases the leukocytes passage through the hematoencephalic barrier and it is currently used in relapsing-remitting forms of multiple sclerosis (MS). We present a patient with allergic rhinoconjunctivitis diagnosed with MS who started treatment with natalizumab. She began to show mild asthmatic symptoms until she needed admission to the hospital due to respiratory insufficiency. Blood tests showed peripheral eosinophilia and the thoracic computed tomography scan demonstrated pulmonary infiltrates. The bronchoscopy with the bronchoalveolar lavage resulted in eosinophilic alveolitis. No evidence of bacterial, fungal and parasitic infection, connective tissue disease, or vasculitis were observed. After discontinuation of natalizumab, the patient improved without other treatments. As MS is a prevalent disease and the use of natalizumab is increasing, we consider important to point out that this drug can be associated with pulmonary eosinophilia, especially in patients with allergic rhinoconjunctivitis or asthma.