Background
Initially described by Löffler in 1932, Löffler syndrome is a transient respiratory illness associated with blood eosinophilia and radiographic shadowing. In 1952, Crofton included Löffler syndrome as one of the 5 categories for conditions that cause pulmonary infiltrates with eosinophilia. The original description of Löffler syndrome listed parasitic infection with Ascaris lumbricoides as its most common cause; however, other parasitic infections and acute hypersensitivity reactions to drugs are included as etiologies for simple pulmonary eosinophilia.