A STUDY OF TROPICAL EOSINOPHILIA

The role of HRCT in Tropical Pulmonary Eosinophilia

PURPOSE

To determine the pattern of pulmonary involvement in clinically confirmed patients of tropical pulmonary eosinophilia (TPE).

METHOD

An observational study on 13 patients with clinically confirmed TPE was performed to determine the CT scan appearances.

RESULTS

The predominant CT scan finding is the presence widespread ill-defined bronchocentric nodules, which need to be differentiated from other conditions.

CONCLUSION

The pattern of lung involvement on a CT scan can give a clue to the diagnosis of TPE in the correct clinical context. Radiologists in tropical countries should have a high index of suspicion for this diagnosis when reading scans showing widespread ill-defined bronchocentric nodules.

Tropical pulmonary eosinophilia--a review

Tropical pulmonary eosinophilia (TPE) is a syndrome of wheezing, fever and eosiniphilia seen predominantly in the Indian subcontinent and other tropical areas. Its etiological link with Wuchereria bancrofti and Brugia malayi has been well established. The pathogenesis is due to an exaggerated immune response to the filarial antigens which includes type I, type III and type IV reactions with eosinophils playing a pivotal role. Peripheral blood eosinophilia is usually striking with levels over 3000/μl being common. High serum levels of IgE and filarial-specific IgE and IgG are also found. The pathology may vary from an acute eosinophilic alveolitis to histiocytic infiltration depending on the stage of the disease. While earlier studies had suggested that the disease runs a benign course, more recent work has shown that untreated TPE could result in a fair degree of respiratory morbidity. Pulmonary function tests may show a mixed restrictive and obstructive abnormality with a reduction in diffusion capacity. The bronchoalveolar lavage (BAL) eosinophil count has a negative correlation with the diffusion capacity. Treatment consists of diethylcarbamazine (DEC) for at least three weeks. Despite treatment with DEC, about 20 per cent of patients may relapse. Steroids have shown to have a beneficial effect but the exact dose and duration is yet to be confirmed by randomized controlled trials. A specific and easily available marker is required for TPE in order to distinguish it from other parasitic and non-parasitic causes of pulmonary eosinophilia.

Recent advances in the diagnosis of Churg-Strauss syndrome

Most pathologists assume that a diagnosis of Churg-Strauss syndrome (CSS) requires the finding of necrotizing vasculitis accompanied by granulomas with eosinophilic necrosis in the setting of asthma and eosinophilia. However, recent data indicate that this definition is too narrow and that adherence to it leads to cases of CSS being missed. CSS has an early, prevasculitic phase that is characterized by tissue infiltration by eosinophils without overt vasculitis. Tissue infiltration may take the form of a simple eosinophilia in any organ, and a fine-needle aspirate showing only eosinophils may suffice for the diagnosis in this situation. The prevasculitic phase appears to respond particularly well to steroids. Even in the vasculitic phase of CSS, many cases do not show a necrotizing vasculitis but often only an apparently nondestructive infiltration of vessel walls by eosinophils. In modern biopsy materials, granulomas frequently cannot be found. In the postvasculitic phase of CSS, healed vascular lesions resemble organized thrombi but typically show very extensive destruction of elastica and, often, an absence of eosinophils. The widespread use of steroids as therapy for asthma has led to the peculiar and confusing situation in which the steroid therapy accidentally suppresses CSS and changes in steroid treatment uncover the disease; this type of "formes frustes" CSS is now well recognized with leukotriene receptor antagonist treatment and will be seen with increasing frequency as other steroid-sparing therapies for asthma are introduced.

[Strongyloides stercoralis infection in patients with bronchial obstructive pathology]

Strongyloides stercoralis infection was hardly seen in Spain until a few years ago but has recently been shown to be fairly common in some geographic areas. In the respiratory tract this germ can cause acute bronchospasms that make diagnosis difficult, particularly in patients with underlying bronchial disease. To determine if curing S. stercoralis infection is accompanied by clinical and functional improvement in patients with bronchial obstruction, we studied the evolution of 22 infected patients: 11 with no bronchopulmonary disease and 11 with chronic airway obstruction or asthma. The following variables were assessed in both groups at the moment of diagnosis of infection and four months after cure: levels of eosinophils and total serum IgE, respiratory symptoms, steroid doses and spirometric parameters. After four months we observed a significant decrease in eosinophil (16 versus 5%) and IgE (1,600 versus 770 IU/ml) levels in both groups. The number of bronchospasms and daily steroid doses required decreased in the group with bronchial disease. No significant differences were seen in spirometric parameters, however. The improvement in respiratory symptoms, blood parameters and need for medication leads us to believe that airway inflammation decreases after the infection has been eradicated, in spite of the lack of improvement in bronchial obstruction.

Cor pulmonale: an unusual presentation of tropical eosinophilia

Tropical pulmonary eosinophilia (TPE) is considered to be a variant of human filarial infection. The pulmonary manifestations of TPE have been well described. Extra-pulmonary features of the disease, although not commonly seen, have been reported previously. A 9-year-old Malay girl with a history of recurrent cough and wheezing was admitted because of cardiac failure. Physical examination revealed a very sick girl with tachypnoea, central cyanosis, finger clubbing, elevated jugular venous pulse, generalized crackles and rhonchi in the chest, a loud second heart sound and hepatosplenomegaly. A chest radiograph showed cardiomegaly and right pleural effusion. Laboratory investigations revealed hypochromic, microcytic anaemia with persistent blood eosinophilia (absolute eosinophil counts varied from 1.9 to 5.5 x 10(9)/1). The ELISA test for antifilarial IgG antibodies was strongly positive. She responded promptly to treatment with diethylcarbamazine. In summary, this is a patient with TPE who presented with cor pulmonale, probably due to late-stage interstitial pulmonary fibrosis. In order to prevent the long term morbidity of cardiorespiratory disability, the early signs of TPE should be recognized and the infection treated.

Tropical pulmonary diseases

The term 'tropical' refers to the region of the Earth lying between the Tropic of Cancer and the Tropic of Capricorn. Located between these equatorial parallels demarcating the Torrid Zone are several underdeveloped and developing countries: Thailand, the Philippines, Malaysia, Singapore, Indonesia, southern India, Sri Lanka, Brazil, Cuba, Ethiopia, Sudan and Nigeria, to name but a few considered to be 'tropical'. The climate in most of these countries is characterized by high temperatures and high humidity. The tropical climate and general state of socio-economic underdevelopment in such countries provide an ideal environment for pathogenic organisms, their vectors and intermediate hosts to flourish. Furthermore, the cultural habits and educational background of the people living in such countries expose them to pathogens and, when these people become infected, they readily become reservoirs for, or carriers of, those organisms. Ultimately, the adverse socioeconomic conditions of underdeveloped countries impede attempts to eradicate or control tropical diseases.

Tropical pulmonary eosinophilia: a comparative evaluation of plain chest radiography and computed tomography

Plain chest radiography and computed tomography (CT) of the chest were performed on 10 patients with tropical pulmonary eosinophilia (TPE). Chest radiographs revealed bilateral diffuse lesions in the lungs of all the patients with relative sparing of lower lobes in one patient. However, computed tomography revealed bilateral diffuse lung lesions in all of the patients with relative sparing of lower lobes in three patients. In seven (70%) of the 10 patients, CT provided additional information. Computed tomography was found to be superior for the detection of reticulonodular pattern, bronchiectasis, air trapping, calcification and mediastinal adenopathy. No correlation was found between pulmonary function and gas exchange data using CT densities. There was also no correlation between the absolute eosinophil count (AEC) and the radiological severity of lesions. In six patients, high-resolution CT (HRCT) was performed in addition to conventional CT (CCT), and nodularity of lesions was better appreciated in these patients. It is concluded from this study that CT is superior to plain radiography for the evaluation of patients with TPE. However, more work needs to be done to substantiate the results of the present study.

Tropical eosinophilia: clinical and physiological response to diethylcarbamazine

Fifty patients with tropical eosinophilia were studied clinically and physiologically, before and after a standard 3-week course of diethylcarbamazine. Before treatment the main physiological abnormality was a reduction in the carbon monoxide transfer factor. One month after the start of treatment most patients had shown a marked symptomatic improvement, but peripheral blood eosinophilia persisted in 52%, radiographic abnormalities in 44%, cough in 22% and chest signs in 8%. Significant improvement was noted in almost all aspects of lung function including blood gases, but the mean values for forced expiratory volume in one second, forced vital capacity, transfer factor and transfer coefficient continued to be significantly lower than predicted values. This study demonstrates the incomplete reversal of clinical, haematological, radiological and physiological changes in tropical eosinophilia one month after starting a 3-week course of diethylcarbamazine.

The course of lung function in treated tropical pulmonary eosinophilia

Poh, S. C. (1974).Thorax, 29, 710-712. The course of lung function in treated tropical pulmonary eosinophilia. A follow-up study over a period of two years in the lung function of 15 patients with tropical pulmonary eosinophilia successfully treated with diethylcarbamazine is reported. A return to normal of the lung function with the exception of the transfer factor and forced expiratory volume is observed by the end of six months and these abnormalities persist up to the end of the study. The possible pathological causes of this defect are discussed.

Pulmonary function in tropical eosinophilia

Pulmonary function studies were carried out on 23 patients with tropical eosinophilia. These showed an obstructive ventilatory defect in patients with symptoms for less than one month, and a restrictive ventilatory defect in addition to obstruction in those with symptoms for one to four months. These findings are correlated with the pathological changes observed by other workers in patients suffering from tropical eosinophilia.