The patient has eosinophilia out of proportion to her symptoms; it did not respond to standard therapy for asthma and should prompt consideration of an alternate diagnosis. The differential diagnosis is quite broad but should include Churg-Strauss syndrome, acute and chronic eosinophilic pneumonia, fungal infections, and tropical pulmonary eosinophilia (TPE). The patient was born in an area endemic for filariasis. TPE occurs in less than 1% of patients with filariasis, but it is common in India, Southeast Asia, the West Indies, Africa, and China.1 It is the result of an immunologic reaction to the microfilariae liberated by gravid Wuchereria bancrofti and Brugia malayi parasites that become trapped in the circulation of the lung. A mosquito vector transmits the microfilariae; adult worms can live up to 10 years within lymph nodes liberating millions of microfilariae. Chest radiography usually reveals reticulonodular opacities, predominantly in the middle and lower lung zones (20% can be normal).2 Computed tomographic scans are more sensitive in detecting abnormalities in this disease. Pulmonary function tests can reveal an obstructive ventilatory defect early in the disease and mixed ventilatory defects in the later stages with decreased diffusion. The diagnosis is established by history of residence in an endemic area, peripheral eosinophilia (> 3 x 103/mm3), elevated total serum IgE level, and elevated parasite-specific IgG4 level. Although the parasites can be found on biopsy specimens, biopsy is rarely necessary to establish a diagnosis. If left untreated, TPE may progress to fibrotic lung disease. Although fiber optic bronchoscopy, bronchoalveolar lavage, transbronchial biopsy, and open lung biopsy can aid in the diagnosis of TPE, they are not necessary to make the diagnosis1; they would be reasonable if results of the work-up for TPE were negative. Stool for ova and parasites are usually negative in TPE unless the patient is coinfected with another parasite. Testing for Aspergillus precipitins would be useful to diagnose an Aspergillus infection, but it would not diagnose TPE.3
- Measure serum IgG4 level.
1. Ong RK, Doyle RL. Tropical pulmonary eosinophilia. Chest 1998;113:1673-9.
2. Udwadia FE. Tropical eosinophilia: a review. Respir Med 1993;87:17-21.
3. Saukkonen JJ. Pulmonary eosinophilia. eMedicine [serial online] 2002. Available at http://www.emedicine.com/MED/topic1959.htm. Accessed 2 Jan 2003.
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