Hypersensitivity Pneumonitis
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Overview
Plain-Language Overview
Hypersensitivity Pneumonitis is a lung condition caused by an allergic reaction to inhaled particles such as mold, bird droppings, or certain chemicals. It affects the lungs, specifically the tiny air sacs called alveoli, leading to inflammation. This inflammation can cause symptoms like cough, shortness of breath, and fatigue. The condition can develop suddenly after exposure or gradually with repeated contact. Over time, if exposure continues, it may lead to permanent lung damage and scarring. The main health impact is difficulty breathing and reduced lung function.
Clinical Definition
Hypersensitivity Pneumonitis is an immune-mediated interstitial lung disease characterized by a type III and type IV hypersensitivity reaction to inhaled organic antigens. It involves alveolitis and granulomatous inflammation primarily affecting the alveoli and small airways. Common triggers include exposure to thermophilic actinomycetes, Saccharopolyspora rectivirgula, bird proteins, and molds. The disease manifests in acute, subacute, or chronic forms, with chronic exposure leading to pulmonary fibrosis. Clinically, it presents with dyspnea, cough, and constitutional symptoms. Diagnosis is important due to potential progression to irreversible lung damage if antigen exposure persists.