† Eosinophil counts up to a maximum of 80 per 100 white blood cells were obtained in seven patients hospitalized for pneumonitis with findings characteristic of Löffler's syndrome, namely, a patchy, migratory infiltration seen in serial roentgenograms. Each patient had received from two to six graded injections of 3-pentadecylcatechol in sesame oil for prophylaxis against poison ivy dermatitis. The symptoms of cough, dyspnea, malaise, and fever set in 8 to 48 hours after the last injection. Sharp chest pains, the production of sputum, occasional rales, and sometimes an inflamed pharynx were among the findings. The only consistent features were the eosinophilia and the pneumonitis. The latter cleared completely in 4 to 15 days.
The phenomena in the lungs may be explained by assuming the existence of a mechanism there for trapping eosinophils. The varying degrees of eosinophilia seen in allergic and parasitic diseases would account for mild, abortive forms of pneumonitis as well as for pulmonary infiltrations massive and dense enough to be revealed by roentgen ray.
Epstein WL, Kligman AM. PATHOGENESIS OF EOSINOPHILIC PNEUMONITIS (LÖFFLER'S SYNDROME). JAMA. 1956;162(2):95–97. doi:10.1001/jama.1956.02970190011003
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