Eosinophilic pneumonia associated with azacitidine in a patient with myelodysplastic syndrome

Eosinophilic pneumonia is characterized by cough, lung infiltrates on imaging, and by the presence of eosinophils in the alveoli and pulmonary interstitium. Azacitidine, a pyramidine nucleoside analog of cytidine, is FDA approved for the treatment of various myelodysplastic syndromes. We present a case of a 76-year-old man with recently diagnosed myelodysplastic syndrome, who developed eosinophilic pneumonia after initiating therapy with azacitidine. There was clinical and radiographic improvement with cessation of the drug and treatment with prednisone. Diagnosis of drug-induced eosinophilic pneumonia is established by having a temporal relationship between onset of symptoms and initiation of therapy, bronchoalveolar lavage or lung biopsy evidence of pulmonary eosinophilia, no other explanation for the disease, and improvement upon cessation of the offending agent. Our case illustrates the need for a high index of suspicion to identify adverse pulmonary reactions associated with newly developed medications.