pulmonary disorders
Hypersensitivity Pneumonitis
Pathophysiology of Hypersensitivity Pneumonitis
The disorder seems to represent a Overview of Allergic and Atopic Disorders , in which repeated exposure to antigen in genetically susceptible people leads to acute neutrophilic and mononuclear alveolitis, followed by interstitial lymphocytic infiltration and granulomatous reaction. Fibrosis with bronchiolar obliteration occurs with continued exposure. Circulating precipitins (antibodies sensitized to antigen) seem not to have a primary etiologic role, and clinical history of allergy (such as asthma and seasonal allergies) is not a predisposing factor. Cigarette smoking seems to delay or prevent development, perhaps through down-regulation of the lung’s immune response to inhaled antigens. However, smoking may exacerbate the disease once established. Hypersensitivity pneumonitis has clinical similarities to other disorders that have different pathophysiologies. Organic dust toxic syndrome (pulmonary mycotoxicosis, grain fever), for example, is a syndrome consisting of fever, chills, myalgias, and dyspnea that does not require prior sensitization and is thought to be caused by inhalation of toxins produced by fungi or other contaminants of organic dust. Silo filler’s disease may lead to Overview of Respiratory Failure , Work-Related Asthma causes dyspnea in people previously sensitized to an inhaled antigen, but features such as airflow obstruction, airway eosinophilia, and differences in triggering antigens distinguish it from hypersensitivity pneumonitis. 