The eosinophilic lung diseases include a heterogeneous group
of rare disorders that share the common feature of eosinophils in
the peripheral blood, BAL, or lung parenchyma.12 Known
causes of pulmonary infiltrates with eosinophilia (PIE) include
parasitic infections and drugs. Loeffler’s syndrome, associated
with minimal respiratory symptoms, migratory infiltrates, and often pronounced
eosinophilia, is now recognized to be caused by parasite larvae
passing through the lungs, especially Ascaris lumbricoides,
but also Ancyclostoma,Echinococcus,Shistosoma, Strongyloides
stercoralis,Necator americanus, and Toxocara species. Generally,
patients respond favorably to thiabendazole or albendazole, although
alternative treatments would include piperazine, levamisole, and
pirantel. Other similar clinical disorders include visceral larva migrans
caused by Toxocara canis and tropical pulmonary
eosinophilic syndrome caused by Wuchereria bancrofti and Brugia
malayi. A large variety of drugs, including penicillin,
cocaine, phenytoin, chlorpromazine, and many others are known to
cause PIE. Patients typically respond favorably to drug elimination
and corticosteroids.
The differential of eosinophilic lung diseases also includes
allergic asthma, allergic bronchopulmonary aspergillosis, acute eosinophilic
pneumonia, chronic eosinophilic pneumonia, Churg-Strauss syndrome, and
idiopathic hypereosinophilic syndrome. The diagnosis of these disorders
is made by identifying eosinophils in peripheral blood, BAL, or
lung biopsy.13 Patients with acute eosinophilic pneumonia
classically present with acute respiratory failure and the notable
absence of peripheral eosinophilia. Therefore, a strong index of suspicion
is necessary, as BAL is required to demonstrate marked eosinophils
in the lung. In these cases, the early institution of corticosteroids
can be lifesaving.