Tropical pulmonary eosinophilia

Last revised by Rohit Sharma on 15 Jan 2024

Tropical pulmonary eosinophilia is a pulmonary condition caused by an overreactive immune response to microfilaria trapped in the lungs. Tropical pulmonary eosinophilia is a distinct entity with specific symptoms and diagnostic criteria that differentiate it from other types of eosinophilia in tropical regions. 

This article discusses tropical pulmonary eosinophilia, a general view of the theme is available in the main article, eosinophilic lung disease

Tropical pulmonary eosinophilia is a disease predominantly limited to tropical regions, with a distribution that overlaps Bancroft's filariasis 1-6. The condition is endemic in large areas of Africa, southern Asia, the Indian subcontinent, the Pacific Islands, and South America 1-6. Sporadic cases may occur in non-endemic countries due to travel or immigration 1-6.

Tropical pulmonary eosinophilia is more common in males than females, particularly in ages 15 to 40 years 1-6

Accurate diagnosis is crucial for the effective management and treatment of tropical pulmonary eosinophilia. Several factors support the filarial etiology of this disease, including 1-6:

  • residence in an endemic area for filariasis

  • nocturnal cough and dyspnea

  • demonstration of microfilariae fragments in lung biopsy material

  • strongly positive complement fixation test for filaria

  • elevated titers of anti-filarial antibodies

  • high serum levels of IgE and filarial-specific IgE and IgG

  • peripheral blood eosinophilia with levels greater than 3000 cells/mm3 or 20%

  • bilateral lung involvement on chest x-ray or CT

  • good therapeutic response to diethylcarbamazine

The clinical presentation of Tropical pulmonary eosinophilia is characterized by the association of hypereosinophilia with bronchitic-asthmatic symptoms, and misdiagnosis as asthma is frequent 1-6

Patients with tropical pulmonary eosinophilia usually present with the following symptoms 1-6:

  • dyspnea, which can be severe and prolonged

  • chronic, paroxysmal cough, more frequent and intense at night 

  • wheeze

  • chest pain due to rib fractures caused by vigorous coughing

  • low fever

  • weight loss

  • fatigue

  • malaise

Tropical pulmonary eosinophilia occurs from a hypersensitivity response to microfilariae antigens, primarily those of Wuchereria bancrofti and Brugia malayi, present in the pulmonary microcirculation, which causes subsequent inflammation with eosinophils playing an essential role 1-6.

The pathology of tropical pulmonary eosinophilia can range from acute eosinophilic alveolitis to histiocytic infiltration and may vary depending on disease severity 1,2,4,6.

The chest radiograph usually shows bilateral and symmetrical pulmonary involvement 1-4. Radiographic findings typically improve with diethylcarbamazine treatment, but residual changes may persist in some patients 1-6. The commonly observed radiological pattern includes 1-6

  • normal chest radiograph

  • bilateral diffuse reticulonodular opacities

  • bilateral miliary nodules

  • global reduction in lung transparency, better demonstrated when compared to normal radiographs obtained after treatment

  • rib fractures, with lower ribs being more commonly affected

The CT is more sensitive and can demonstrate in more detail the radiological abnormalities 1,3-5:

To effectively manage tropical pulmonary eosinophilia and prevent long-term respiratory complications, a timely and accurate diagnosis followed by treatment is crucial 1-6. Diethylcarbamazine is used to treat filariasis, including tropical pulmonary eosinophilia 1-6. Without treatment, patients may develop interstitial lung disease 1-6.

Tropical pulmonary eosinophilia was first reported in India in 1940 by Frimodt-Moller and Barton, who described the association of hypereosinophilia, bronchitic-asthmatic-like symptoms, and pulmonary infiltrates on chest x-rays 2,4,5. In 1943, Weingarten named the disease and described its clinical and radiological features 2,4,5.

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