Extrinsic allergic alveolitis (hypersensitivity pneumonitis)
Journal Title: Postępy Nauk Medycznych - Year 2011, Vol 24, Issue 4
Abstract
Extrinsic allergic alveolitis (EAA, also: hypersensitivity pneumonitis – HP) is an inflammatory lung disease caused by environmental antigens of different source: bacterial, fungal, animal or chemical. It is characterized as type III (immune complexes) and type IV (delayed cellular infiltrates) hypersensitivity reaction. Histologically, lymphocytic infiltrates, poorly defined granulomas, bronchiolitis and fibrotic pattern are present. Lymphocytes predominate in broncho-alveolar lavage fluid and they may constitute over 50% of cell count. EAA is traditionally divided on clinical grounds into acute, subacute and chronic stages. In acute stage flu – like symptoms are present: fever, chills, dry cough, dyspnoea, bone and muscle pain. Subacute and chronic stages are characterized by progressive dyspnoea and exercise intolerance. On examination bilateral basal crepitations are present, clubbing is rare. In some patients precipitins against causative antigens may be found, but diagnosis does not relay on positive test. Patchy and nodular opacities are found on plain chest X-ray and high resolution computed tomography shows centrilobular nodules, diffuse ground glass opacities and fibrosis. Pulmonary function tests reveal restrictive pattern with decreased diffusion capacity of the lungs and hypoxemia on exertion. The most effective treatment is avoiding antigen exposure. In some severe and chronic cases systemic steroids may be useful. Prognosis is good in most cases of acute and subacute stages, but chronic HP may produce lung fibrosis and respiratory failure.
Authors and Affiliations
Katarzyna Lewandowska
Keywords
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