Tropical pulmonary eosinophilia is a cause of eosinophilic pneumonia in patients who have lived in the tropics. This syndrome is felt to be due to immune hyperresponsiveness in patients infected with the filarial parasites Wuchereria bancrofti, Brugia malayi, or Brugia timori.

These agents are responsible for lymphatic filariasis (chronic lymphatic dysfunction following infection can lead to progressive lymphedema and swelling of the extremities or genitalia). They are transmitted by mosquitoes in tropical and subtropical areas of South America, Southeast Asia, India, and Africa. Of patients with filariasis, it is estimated that fewer than 1% develop tropical pulmonary eosinophilia. It affects more males than females, and most patients are between the ages of 15 and 40, although it is most common in young adults.

Patients with tropical pulmonary eosinophilia present with cough, wheezing, and dyspnea. Symptoms may be most pronounced at night. Patients may have extrapulmonary signs and symptoms including lymphadenopathy and hepatosplenomegaly as well as weight loss, malaise, and fatigue.

Laboratory evaluation may reveal peripheral eosinophilia, and levels are commonly elevated in the >3000/μL range. Immunoglobulin E (IgE) levels are also often elevated (>1000 units/mL). Chest radiograph may reveal increased interstitial markings with small pulmonary nodules. The mid- and lower lungs are most affected. Interstitial fibrosis may occur if this condition is not treated.

Treatment is with diethylcarbamazine.