Breathlessness with cough, malaise, and fever

A 62 year old woman presented with shortness of breath that had gradually worsened in three months. She had a productive cough of the same duration, intermittent fevers, malaise, and mild weight loss. She had no relevant occupational or drug history but had kept a budgerigar (parakeet) for the past 18 months.

On examination, her breath sounds were vesicular with no added sounds. A chest x ray (fig 1) and a high resolution computed tomogram (fig 2) were taken.

Fig 1 Posteroanterior chest radiograph of patient at presentation

Fig 2 Selected window from high resolution computed tomogram of the thorax. The image is taken at the level of the division of the right middle and lower bronchi, showing the mid-zones of the lungs. The oblique fissure of the left lung can be seen

Questions

(1) What does the chest x ray scan (fig 1) show?

(2) What does the high resolution computed tomogram (fig 2) show?

(3) What is the differential diagnosis and what is the most likely diagnosis?

(4) What tests might help to confirm your diagnosis?

(5) What treatment would you suggest?

Answers

(1) The posteroanterior chest radiograph in fig 1 indicates bilateral mid-zone opacification (as shown by the arrows).

(2) The computed tomogram in fig 2 shows bilateral patchy centrilobular opacification and ground glass opacification (as shown by the arrows). There are no features of fibrosis, such as interlobular or intralobular septal thickening or honeycomb cysts.

(3) The differential diagnosis from the images is wide. Ground glass changes are non-specific and result from some degree of alveolar wall thickening or from partial filling of the alveolar space with fluid or cells. Given the context, the most likely differential is hypersensitivity pneumonitis (also known as extrinsic allergic alveolitis), although sarcoidosis is another possibility.

The clinical history and the characteristic computed tomogram are strongly indicative of hypersensitivity pneumonitis caused by exposure to birds (bird fancier’s lung). The computed tomogram changes typically affect the middle and upper zones with relative sparing of the lower zones. Inspiratory crackles are often heard on auscultation, but the chest can be clear, as in this case.

(4) Immunological assays may help. Here assays for autoantibodies were negative, but the patient was positive for avian precipitins.

(5) Find an alternative home for the budgerigar and remove or clean carpets and soft furnishings if possible. Corticosteroids may be needed if the patient has particularly severe disease.

Discussion

Hypersensitivity pneumonitis is an infiltrative pulmonary disorder that arises from the inhalation of organic dust.¹ This trigger results in the formation of immune complexes that activate an inflammatory response in small airways (bronchiolitis) and the lung interstitium. Small poorly formed granulomas are also a pathological feature of hypersensitivity pneumonitis.

The disease can be acute, subacute (as in this case), or chronic.¹ Although in the United Kingdom hypersensitivity pneumonitis is usually referred to as extrinsic allergic alveolitis, forthcoming British Thoracic Society guidelines will adopt the term hypersensitivity pneumonitis in keeping with internationally accepted nomenclature.

Diagnosis

The diagnosis depends upon a detailed history of occupational or environmental exposure that raise suspicion of hypersensitivity pneumonitis.

The insidious onset of breathlessness and the radiological abnormalities in a person exposed to birds is typical of bird fancier’s lung, an immune mediated reaction to avian serum proteins contained in bird feathers and excreta. The other symptoms that the patient experiences—cough, malaise, and fever—are also typical of hypersensitivity pneumonitis. Indeed, insidious onset of symptoms, as seen here, is more commonly seen in bird fancier’s lung arising from exposure to household pets, rather than from industrial exposure to avian proteins.^{1 2}

The combination of characteristic clinical and imaging findings together with a potential source of antigen forms the basis for the diagnosis. The presence of IgG antibodies (precipitans) to the specific antigen indicates exposure but not necessarily disease. Bronchoalveolar lavage typically shows excess lymphocytes, and a surgical lung biopsy may be needed to confirm the diagnosis.²

Management

For subacute and more chronic presentations, as described here, avoiding exposure to the precipitating antigen is essential.¹ In such cases removing the birds would be advisable. Complete recovery after cessation of exposure is usual, although if exposure to the antigen is prolonged, a permanent interstitial fibrosis may develop.

An acute episode of hypersensitivity pneumonitis may require admission, high flow oxygen, and a tapering course of oral prednisolone. Longer term management of acute attacks also involves avoidance of the allergen.¹

We thank John Simpson and John Murchison for invaluable advice.

1. Ismail T, McSharry C, Boyd G. Review article: extrinsic allergic alveolitis. Respirology 2006;11:262-8.
2. Fink J, Ortega H, Reynolds H, Cormier YF, Fan LL, Franks TJ, et al. Needs and opportunities for research in hypersensitivity pneumonitis. Am J Respir Crit Care Med 2005;171:792-8.

       

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