(See also Overview of Eosinophilic Pulmonary Diseases.)
Chronic eosinophilic pneumonia is not truly chronic; rather it is an acute or subacute illness that recurs (thus, a better name might be recurrent eosinophilic pneumonia). The prevalence and incidence of chronic eosinophilic pneumonia are unknown. Etiology is suspected to be an allergic diathesis. Most patients are nonsmokers.
Patients with chronic eosinophilic pneumonia often present with fulminant illness characterized by cough, fever, progressive breathlessness, wheezing, and night sweats. The clinical presentation may suggest a community-acquired pneumonia. Asthma accompanies or precedes the illness in > 50% of cases. Patients with recurrent symptoms may have weight loss.
Diagnosis of chronic eosinophilic pneumonia is suspected in patients with characteristic symptoms and typical radiographic appearance.
Diagnosis also requires a complete blood count (CBC), erythrocyte sedimentation rate (ESR), sometimes iron studies, and exclusion of infectious causes by appropriate cultures. Peripheral blood eosinophilia, a very high ESR, iron deficiency anemia, and thrombocytosis are all frequently present.
Chest x-ray findings of bilateral peripheral or pleural-based opacities, most commonly in the middle and upper lung zones, are described as the photographic negative of pulmonary edema and are virtually pathognomonic (although present in < 25% of patients). A similar pattern can be present on HRCT, but the distribution of consolidation can vary and even include unilateral lesions.
Bronchoalveolar lavage is usually done to confirm the diagnosis. Eosinophilia > 40% in bronchoalveolar lavage fluid is highly suggestive of chronic eosinophilic pneumonia; serial bronchoalveolar lavage examinations may help document the course of disease.
Patients with chronic eosinophilic pneumonia are uniformly responsive to IV or oral corticosteroids; failure to respond suggests another diagnosis. Initial treatment is prednisone 40 to 60 mg once a day. Clinical improvement is frequently striking and rapid, often occurring within 48 hours. Complete resolution of symptoms and x-ray abnormalities occurs within 14 days in most patients and by 1 month in almost all.
Symptoms and plain chest x-rays are both reliable and efficient guides to therapy. Although HRCT is more sensitive for the detection of imaging abnormalities, there is no benefit gained by repeating CT.
Peripheral eosinophil counts, ESR, and IgE levels can also be used to follow the clinical course during treatment. However, not all patients have abnormal laboratory test results.
Symptomatic or radiographic relapse occurs in many cases either after cessation of therapy or, less commonly, with tapering of the corticosteroid dose. Relapse can occur months to years after the initial episode. Thus, corticosteroid therapy may be required for long periods of time (years). Inhaled corticosteroids (eg, fluticasone or beclomethasone 500 to 750 mcg twice a day) may be effective, especially in reducing the maintenance dose of oral corticosteroid.
Relapse does not appear to indicate treatment failure, a worse prognosis, or greater morbidity. Patients continue to respond to corticosteroids as during the initial episode. Fixed airflow obstruction can occur in some patients who recover, but the abnormalities are usually of borderline clinical significance.
Chronic eosinophilic pneumonia occasionally leads to physiologically important restrictive lung function abnormalities as a result of irreversible fibrosis, but abnormalities are usually mild enough that this disorder is an extremely unusual cause of morbidity or death.