|Year : 2013 | Volume
| Issue : 1 | Page : 52-54
Fluorodeoxyglucose positron emission tomography in tropical pulmonary eosinophilia presenting as interstitial lung disease
Ketaki Satish Barve1, Sandip Basu2, Jyotsna M Joshi1
1 Department of Pulmonary Medicine, Topiwala National Medical College, B. Y. L. Nair Hospital, Mumbai, India
2 Radiation Medicine Centre (Bhabha Atomic Research Centre), Tata Memorial Hospital Annexe, Parel, Mumbai, India
|Date of Web Publication||17-Aug-2013|
Jyotsna M Joshi
Department of Pulmonary Medicine, Topiwala National Medical College and B. Y. L. Nair Hospital, Mumbai - 400 008
Source of Support: None, Conflict of Interest: None
The role of fluorodeoxyglucose positron emission tomography (FDG-PET) is being increasingly recognized and investigated as a functional imaging technique to explore nonmalignant thoracic disorders. We report a case of a 72-year-old woman who presented as interstitial lung disease (ILD) due to tropical pulmonary eosinophilia (TPE). FDG-PET helped in confirming disease activity and response to treatment with diethyl carbamazine (DEC). The role of FDG-PET in TPE has not been reported previously.
Keywords: Chest radiograph, Donohugh′s criteria, high resolution computerized tomography
|How to cite this article:|
Barve KS, Basu S, Joshi JM. Fluorodeoxyglucose positron emission tomography in tropical pulmonary eosinophilia presenting as interstitial lung disease. Indian J Allergy Asthma Immunol 2013;27:52-4
|How to cite this URL:|
Barve KS, Basu S, Joshi JM. Fluorodeoxyglucose positron emission tomography in tropical pulmonary eosinophilia presenting as interstitial lung disease. Indian J Allergy Asthma Immunol [serial online] 2013 [cited 2017 Mar 27];27:52-4. Available from: http://www.ijaai.in/text.asp?2013/27/1/52/116610
| Introduction|| |
Tropical pulmonary eosinophilia (TPE) is a form of occult filariasis causing interstitial lung disease (ILD) due to a heightened immunological response to human filarial parasite Wuchereria bancrofti and Brugia malayi.  TPE has been reported from endemic regions all over the world; but Indians are more frequently affected than other ethnic groups. Patients are mainly in younger age group (20-40 years) and there is male predominance.  Characteristic presentations include paroxysmal cough, dyspnea, nocturnal wheezing and occasionally fever, anorexia, and weight loss.  Diagnostic criteria given by Donohugh  help in making a diagnosis. They are residence in tropics with presence of eosinophil count of >3,000, absence of microfilaria in peripheral blood, raised serum immunoglobulin E (IgE) >1,000 U, elevated titers of microfilarial antibodies and response to diethyl carbamazine (DEC) given in a dose of 6 mg/kg/day for 3 weeks.
Fluorodeoxyglucose positron emission tomography (FDG-PET) is a promising functional imaging technique that has been primarily utilized for studying malignant conditions. However, gradually the potential of its use has been recognized and explored in certain benign conditions as well. Here we highlight the role of FDG-PET in a case of TPE presenting as ILD.
| Case Report|| |
A 72-year-old woman, nonsmoker, resident of Mumbai presented with 4-month history of dry cough and progressive dyspnea. Her vital parameters were normal with pulse oximetry saturation of 91% on room air. Post exercise desaturation was present. Chest auscultation revealed bilateral crackles. Laboratory investigations were within normal limits except for a high total eosinophil count (TEC) of 4,704/mm 3 . Serum IgE was raised (16,780 U). Chest radiograph showed bilateral reticulonodular opacities [Figure 1]. High resolution computerized tomography (HRCT) [Figure 2] showed areas of intralobular and interstitial septal thickening involving bilateral lung parenchyma showing a peripheral distribution pattern. Spirometry showed a restrictive abnormality with forced vital capacity (FVC) of 0.57 L (32% predicted); forced expiratory volume in first second (FEV 1 ) 0.49 L (34% predicted); and FEV 1 /FVC ratio 85%. Filarial antibody test was positive while peripheral smear showed absence of microfilaria. FDG-PET scan [Figure 3] was performed and showed multiple tiny foci scattered over mid and lower zones of both lungs. A diagnosis of TPE was made and the patient was treated with DEC for a total duration of 21 days. Following treatment her symptoms improved, clinical examination was normal, there was no exercise desaturation, TEC was reduced to 1020/mm 3 , and spirometry improved to FVC 1.52 (84% predicted); FEV 1 1.46 (101% predicted). Our case fulfilled all five of Donohugh's criteria, which confirmed the diagnosis of TPE. Repeat posttreatment chest radiograph [Figure 4], HRCT [Figure 5] significant clearing of the opacities while FDG-PET [Figure 6] showed complete resolution of uptake in the pulmonary parenchyma bilaterally.
|Figure 2: (a and b) High resolution computed tomography (HRCT) showing bilateral intralobular interstitial and septal thickening with peripheral predominance|
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|Figure 3: Fluorodeoxyglucose positron emission tomography (FDG-PET) scan showing multiple tiny foci of uptake scattered over mid and lower zones of both lungs|
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|Figure 4: Posttreatment chest radiograph showing clearing of the opacities|
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|Figure 6: Posttreatment FDG-PET showing resolution of uptake in the pulmonary parenchyma bilaterally|
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| Discussion|| |
TPE can mimic many other conditions. Cases of TPE are frequently misdiagnosed as asthma, miliary tuberculosis, and idiopathic ILDs. Unless there is a high index of suspicion, the condition can be easily missed. The present case serves as a reminder that diagnosis of TPE should be considered in a patient with micronodular opacity on the chest radiograph along with eosinophilia. It has been observed that the disease if left untreated or treated late, may lead to long-term sequelae or pulmonary fibrosis, chronic bronchitis, or chronic respiratory failure.
Chest radiographic findings in TPE include reticulonodular opacities mainly in the middle and lower zones, miliary mottling, and prominent hila with increased vascular markings. Chest radiographs may be normal in 20% of patients.  HRCT has been shown to be better in detecting nodularity, fibrosis, bronchiectasis, air trapping, mediastinal adenopathy, and calcification.  Pulmonary function tests show restrictive pattern in majority of cases although it may show obstructive ventilatory defect early in the illness. 
FDG-PET has been primarily used for diagnosis of malignant conditions based upon the principle of Warburg's effect in tumor cells leading to increased glucose uptake. The increased FDG uptake in tumors is multifactorial but mainly related to glucose transporter (GLUT 1 and 3) over expression,  Hexokinase overactivity and  paucity of glucose-6-phosphatase activity in the tumor cells. Similar to tumor cells, inflammatory cells demonstrate enhanced GLUT activity under cytokine stimulation. TPE has been shown to have inflammation histopathologically before commencement of treatment which could explain FDG hypermetabolism in this disorder. It ranges from histiocytic inflammation in alveolar, interstitial, peribronchial, and perivascular spaces in early stages (1-2 weeks) to chronic mixed inflammation in nodular pattern and development of pulmonary fibrosis in late stages without treatment.
To the best of our knowledge, the role of FDG-PET in the setting of TPE has not been described in peer-reviewed literature. Kim et al.,  have reported FDG-PET in simple pulmonary eosinophilia where diagnosis of simple pulmonary eosinophilia was made retrospectively with the help of FDG-PET based on transient nature of pulmonary nodule, patients symptoms, and eosinophilia. Presence of FDG uptake in our patient in the initial study indicates inflammation and presence of disease activity while resolution of uptake on posttreatment scan is suggestive of decreased disease activity, and hence response to treatment.
We conclude that FDG-PET can potentially find use in evaluating disease activity and response to treatment in TPE. Further studies are required to define its precise clinical role in TPE and its utility in assessing treatment response. Also, it is an observational study and of research interest and is not cost-effective.
| Acknowledgment|| |
The authors would like to thank Dr. Bhavin Jankharia, Consultant Radiologist, Piramal Diagnostics-Jankharia Imaging, Mumbai, India for the CT images.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]