Exogenous allergic alveolitis

Exogenous allergic alveolitis (or hypersensitive pneumonitis, farmer's lung, pigeon's lung) includes a group of immunologically conditioned diseases (type III. hypersensitivity) with granulomatous inflammation in the bronchioles and alveoli. It is an interstitial pulmonary fibrosis caused by repeated contact with certain allergens. The most endangered group are workers of plant and animal production after repeated exposure to moldy hay, straw and grain. Exogenous allergic alveolitis also occurs while working with moldy malt, furs, moldy cheese, feather and bird excrement. It is rare in children and is most often caused by inhalation of organic dust from birds (pigeons, parrots, budgies).

Diagnostics

 * Patient's history, laboratory signs of inflammation, precipitating antibodies (specific IgG) in serum against including antigen
 * Chest X-ray: reticulonodular drawing with mottled volatile infiltrates
 * BAL: usually lymphocytic alveolitis, ↓ CD4/CD8
 * Chronic phase: X-ray + HRCT image of interstitial pulmonary fibrosis/honeycomb lung; restriction, lung diffusion capacity disorder, hypoxemia; lung biopsy.

Clinical picture
The acute form is reversible and develops within about 6 hours after intense antigen exposure. It expires within 48 hours. Physically, crepitus above the lung bases is demonstrable. The following characteristics are manifested: If antigen exposure persists, a chronic form of exogenous allergic alveolitis develops. In case of repeated exposure, lower concentrations of the respective antigen are also sufficient. Irreversible interstitial lung fibrosis (restriction disorder) occurs. The symptoms are:
 * Acute:
 * paroxysmal cough, fever, chill, malaise, myalgia, headache.
 * Chronic:
 * weight loss, fatigue, cough, dyspnoea and cyanosis, cor pulmonale, clubbed fingers, respiratory failure.

Therapy

 * Elimination of antigens – necessary permanent exclusion of the workers from exposure (for occupational diseases)
 * corticoids
 * oxygen therapy.

Related articles

 * Chronická onemocnění plic • Intersticiální plicní procesy • Alergická onemocnění dýchacího ústrojí