Chronic eosinophilic pneumonia is a rare, idiopathic disease characterized by an abnormal and marked accumulation of eosinophils in the interstitium and alveolar spaces in the lung, typically affecting patients in their 30s and 40s. Approximately 60% of patients have a history of atopy, and 50% have preceding asthma or will go on to develop asthma.

Patients typically present with several months of gradual onset of symptoms including fever, dyspnea, productive cough, weight loss, and night sweats. Physical examination may reveal wheezing or crackles in approximately 1/3 of patients. Prognosis is generally quite good despite relapses and the need for long-term therapy.