Raj Kumar1, Mandeep Singh2

1Department of Respiratory Allergy and Applied Immunology, National Centre of Respiratory Allergy, Asthma, and Immunology, Delhi, India

2Senior Resident, V.P Chest Institute, Delhi, India

Bird fancier’s lung: clinical-radiological presentation in 15 cases

Płuco hodowców ptaków: kliniczno-radiologiczna prezentacja 15 przypadków

The authors declare no financial disclosure

Introduction

Hypersensitivity pneumonitis is a pulmonary disease with symptoms of dyspnoea and cough resulting from the inhalation of an antigen contained in certain organic dusts to which the patient has been previously sensitised. The two most well known types of hypersensitivity pneumonitis are farmer’s lung and bird fancier’s lung — especially due to pigeons [1]. Bird fancier’s lung (BFL) is a type of hypersensitivity pneumonitis occurring in response to avian antigens (usually inhaled proteins in bird feathers and droppings) in susceptible subjects [2] In a population-based study from the United Kingdom, the incidence of hypersensitivity pneumonitis was found to be 1 per 100,000 in the general population [3] while the prevalence of clinical disease in those regularly exposed to pigeons has been estimated to be 1 per 1,000. [4] The diagnosis is based on a combination of clinical, radiological, and biopsy characteristics. The aim of the present study is to assess the clinical, radiological, and pulmonary function testing including diffusion and histology in a sub-group of chronic hypersensitivity pneumonitis patients due to exposure to pigeons.

Material and methods

The present study is a retrospective analysis of cases of bird fancier’s lung diagnosed in a unit of Vallabhbhai Patel Chest Institute over a period of two years from 2013−2014. All patients had their detailed clinical history recorded in file and excel sheet. High-resolution computed tomography (HRCT) of the chest and bronchoscopy were performed in all subjects. The diagnosis of bird fancier’s lung due to pigeons was based on criteria laid down by Mark Schuyler and Yvon Cormier [5]. The diagnostic criteria followed are discussed in Table 1. Spirometry along with lung volume and diffusion studies were carried out in all the patients, and the results were classified as per ATS/ERS interpretative strategies for lung function testing. Severity of spirometric abnormality was graded based on percentage of predicted FEV1 as mild (FEV1 > 70% predicted), moderate (FEV1 60−69% predicted), moderately severe (FEV1 50–59% predicted), severe (FEV1 35−49% predicted), or very severe (FEV1 < 35% predicted). Severity of diffusion impairment was graded as mild > 60% and < lower limit of normal, moderate 40–60%, and severe < 40% predicted [6]. Bronchoscopy was performed under local anaesthesia with xylocaine 2% and various bronchoscopic procedures performed as per requirement of the case.

Results

There were a total of 15 cases diagnosed with bird fancier’s lung during the study period. During the same time, 115 cases of interstitial lung disease were diagnosed, thus representing about 13% of interstitial lung disease burden. The age of subjects varied from 29 to 82 years. The details of these patients are summarised in Table 2.

All the studied subjects gave significant history of exposure to pigeons. The majority of these patients were involved in the gaming and rearing of pigeons and regularly used to clean the faecal matter of these birds. Significantly, all the diagnosed subjects were non-smokers.

Most of the patients had a long subdued course of symptoms before presentation, with exertional breathlessness (100%) and dry cough (93.3%) being the most common symptoms. Other symptoms at presentation in patients were low-grade fever and myalgia in 60% of subjects. One of the patients had received a full course of anti-tuberculosis therapy for sputum positive tuberculosis in the past. Of note, there was a mean diagnostic delay of four years from symptom onset.

The pulmonary function tests were abnormal in all except one case. The predominant abnormality was the presence of restrictive lung disease (12 cases, 80%) while obstruction, isolated impairment of diffusion capacity, and normal lung functions were each seen in one case. The diffusion capacity was reduced in 13 cases with most of the subjects having moderate decrease in diffusion capacity and an average diffusion capacity of 52.86 + 9.77 per cent of predicted value.

Radiologically, diffuse centrilobular nodules — ground glassing diffuse or patchy, predominant in the upper lobes, fibrosis with or without traction bronchiectasis, honeycombing, and mediastinal lymphadenopathy were the various findings observed (Fig. 1). The relative frequency of each finding is summarised in Table 2. The honeycombing, observed in two cases, was limited to the upper lobes with relative sparing of the lower lobe. The mediastinal lymphadenopathy observed in two cases was seen in the pre-carinal and para-aortic group. In one patient with prior history of anti-tuberculosis therapy, multiple right upper lobe cavities were seen.

Figure 1. High-Resolution Computed Tomography chest characteristics; A — irregular lines; B — centrilobular nodules; C — diffuse ground glass; D — patchy ground glass; E — honeycombing; F — traction bronchiectasis; G — para-aortic mediastinal lymphadenopathy; H — pre-carinal mediastinal lymphadenopathy

The tracheobronchial tree was normal on gross bronchoscopic inspection in all cases. Transbronchial lung biopsy was done in all cases, from the most involved areas as suggested by computed tomography. Transbronchial lung biopsies showed ill-defined granulomas in 60% (9/15) of cases and chronic interstitial inflammation in 87% (13/15) cases (Fig. 2).

Figure 2. Chronic interstitial infiltrate with ill-defined granuloma

Discussion

Pigeon-breeder’s lung was first reported in 1965 by Reed et al. [7]. The prevalence rates of pigeon-related hypersensitivity pneumonitis was found to be 1−10% in people highly exposed to pigeons [8, 9]. In the present study all the diagnosed subjects gave significant history of exposure to pigeons. Hypersensitivity pneumonitis is known to contribute to 5−15% of ILD burden [10]. Cigarette smoke is believed to have an immunosuppressive effect on alveolar macrophages and thus hypersensitivity pneumonitis is less common in smokers [8]. This is consistent with our study, in which all the diagnosed subjects were non-smokers.

The long duration of symptoms prior to symptom onset (average four years) seen in the present study, as well as in other studies [11], highlights the potential for diagnosing disease in its early stages before irreversible fibrosis sets in. The early symptoms of dry cough and exertional breathlessness along with myalgia are non-specific, and it is essential to take a detailed exposure history in every clinical presentation suggestive of interstitial lung disease to avoid late diagnosis.

The pattern on HRCT chest was the characteristic combination of ground-glass opacification, poorly defined centrilobular nodules, and/or irregular lines. The irregular lines representing fibrosis further led to traction bronchiectasis and non-specific honeycombing in two cases. The honeycombing seen in our cases was different from that of idiopathic pulmonary fibrosis by its presence in the upper lobes. An absence of lower lobe predominance has been used to distinguish hypersensitivity pneumonitis from idiopathic pulmonary fibrosis in some studies [11, 12]. The comparison of the radiological findings between the present study and some of the other studies [11, 13, 14] in literature are presented in Table 3.

Restrictive ventilator defect was the predominant spirometric abnormality seen in 80% of cases while 6% each showed obstruction, isolated diffusion impairment, and normal lung function. In a study by Morell [11], restrictive defect was seen in 77% of cases, similar to that in our study.

The histology on transbronchial lung biopsy showed chronic interstitial infiltrate in 87% of cases while ill-defined granulomas were seen in 60% of cases. VATS or open lung biopsies are more reliable but seldom necessary [11, 15]. The characteristic histological triad of the following: a) interstitial infiltrates of lymphocytes and plasma cells, b) bronchiolitis obliterans, and c) tiny interstitial loosely-formed non-necrotising granulomas, is specific but is usually not found in chronic hypersensitivity pneumonitis [11]. In a study by Moore et al. [11] the characteristic histological triad was found in only 9% of cases while lymphocytic-histiocytic infiltrate was seen in 67% and poorly formed granulomas in 21% of cases by transbronchial lung biopsy.

The essential treatment in hypersensitivity pneumonitis is avoidance of suspected antigens. Achieving this objective can sometimes be far from simple. In developing countries like India, pigeons often cohabitate with humans, making antigenic avoidance impossible. Apart from antigen avoidance, corticosteroids in starting doses of 0.5−0.75 mg/kg/day are usually given in tapering doses over 3-6 months with variable effect on the disease progression.

Conclusions

Bird fancier’s lung has a wide range of radiological patterns. A high index of suspicion must be maintained and utmost attention paid to taking detailed exposure history in every case of interstitial lung disease. The greatest challenge in hypersensitivity pneumonitis cases, as pointed out by Merrill [16], is for the clinician to consider that hypersensitivity pneumonitis is among the possible diagnoses.

Conflict of interest

The authors declare no conflict of interest.

Address for correspondence: Prof. Raj Kumar, MD, Department of Respiratory Allergy, and Applied Immunology, National Centre of Respiratory Allergy, Asthma, and Immunology, V P Chest Institute, University of Delhi, Delhi 110007, India, Tel.: 9810146835; 91-011-27667667, Ext. 144, Fax: 91-011-27667420, e-mail: rajkumarvpci@gmail.com

DOI: 10.5603/PiAP.2015.0005

Received 9.09.2014

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