In 1943, Weingarten and others first discovered tropical pulmonary eosinophilia, also known as tropical eosinophilia or Weingarten syndrome, in regions such as India and Sri Lanka. Subsequently, it has been identified in Africa, Latin America, Southeast Asia, and southern China. This condition is primarily associated with filarial infection, is more common in males than females, and predominantly affects young adults.

bubble_chart Etiology

There is already sufficient evidence indicating a close relationship between this condition and filarial infection. For instance, the complement fixation test for filarial antigens is positive in the serum of the vast majority of patients, with titers decreasing after treatment; microfilariae have been found in the liver, lungs, and lymph nodes of typical patients; and anti-filarial drug therapy has shown good efficacy for this condition. Some other parasitic infections, such as ascariasis, hookworm, and Toxocara infection, may also cause this condition.

bubble_chart Pathological Changes

The lung tissue exhibits diffuse infiltration of histiocytes and eosinophils, which may form eosinophilic abscesses. Reports have mentioned finding microfilariae and their residual skeletons at the center of pulmonary lesions. In advanced stages, the lesions may become fibrotic and cause pulmonary function impairment.

bubble_chart Clinical Manifestations

Common clinical symptoms include cough, wheezing, chest tightness, lack of strength, anorexia, and fever. The cough is severe, but the sputum is thick and sticky, making it difficult to expectorate, and sometimes there is blood in the sputum. Asthma-like episodes may occur. A few patients may experience arrhythmias and digestive system manifestations. Without effective treatment, the course of the disease often becomes prolonged and recurrent, and after several years, manifestations of pulmonary insufficiency may appear due to pulmonary fibrosis. Physical examination may reveal wheezing sounds in the lungs and grade I hepatomegaly, splenomegaly, and lymphadenopathy. Laboratory tests show a significant increase in peripheral blood eosinophils, which may exceed 2,500/mm³

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Chest X-ray findings include foxtail millet-like granular or hazy shadows, predominantly distributed in the middle and lower lung fields bilaterally. After treatment, the abnormal lung X-ray findings may disappear quickly. However, chronic patients often develop residual pulmonary interstitial fibrosis.

bubble_chart Diagnosis

The diagnosis can be made based on the disease's frequent occurrence in filariasis-endemic areas, symptoms such as paroxysmal cough and asthma, and a significant increase in peripheral blood eosinophils. A positive microfilarial complement fixation test confirms the diagnosis. Sometimes, relying solely on clinical manifestations may lead to misdiagnosis as bronchial asthma or confusion with other PIE. A rapid response to diagnostic treatment with hetrazan can aid in differential diagnosis.

bubble_chart Treatment Measures

Diethylcarbamazine is the drug of choice for this condition, administered at 6–8 mg/kg/day in three divided oral doses for 10–14 days, with symptoms often alleviated within days. Other optional medications include levamisole, carbarsone, and acetyllarsan. The time required for eosinophil counts and X-ray changes to return to normal is typically slower than the resolution of clinical symptoms, usually taking 1–3 months. Some patients may experience symptom exacerbation during the initial stage of treatment, in which case prednisone can be co-administered for several days. Approximately 20% of cases may relapse several years after the aforementioned treatment, leading some authors to recommend repeating the course 2–3 times with one-month intervals between courses to prevent recurrence.