Inﬂammation of the alveoli (see ALVEOLUS) of the lungs caused by an allergic reaction. When the inﬂammation is caused by infection it is called PNEUMONIA, and when by a chemical or physical agent it is called pneumonitis. It may be associated with systemic sclerosis or RHEUMATOID ARTHRITIS.
Extrinsic allergic alveolitis is the condition induced by the lungs becoming allergic (see ALLERGY) to various factors or substances. It includes BAGASSOSIS, FARMER’S LUNG and BUDGERIGAR-FANCIER’S LUNG, and is characterised by the onset of shortness of breath, tightness of the chest, cough and fever. The onset may be sudden or gradual. Treatment consists of removal of the aﬀected individual from the oﬀending material to which he or she has become allergic. CORTICOSTEROIDS give temporary relief.
Fibrosing alveolitis In this disease there is diﬀuse FIBROSIS of the walls of the alveoli of the lungs. This causes loss of lung volume with both forced expiratory volume and vital capacity aﬀected, but the ratio between them remaining normal. The patient complains of cough and progressive DYSPNOEA. Typically the patient will be cyanosed (blue – see CYANOSIS), clubbed (see CLUBBING), and have crackles in the mid- and lower-lung ﬁelds. Blood gases will reveal HYPOXIA and, in early disease, hypocapnia (deﬁciency of carbon dioxide in the blood due to hyperventilation). There is an association with RHEUMATOID ARTHRITIS (about one-eighth of cases), systemic lupus erythematosus (see under LUPUS), and systemic SCLEROSIS. Certain drugs – for example, bleomycin, busulphan and hexamethonium – may also cause this condition, as may high concentrations of oxygen, and inhalation of CADMIUM fumes.