POLYMORPHONUCLEAR LEUCOCYTE COUNT is raised in acute cases.
PRECIPITATING ANTIBODIES are present in the serum. One-quarter of pigeon fanciers have precipitating antibody against pigeon protein and droppings in their serum but only a small proportion have lung disease. Precipitating antibodies are evidence of exposure, not disease.
LUNG FUNCTION TESTS show a restrictive ventilatory defect with a decrease in gas transfer.
BRONCHOALVEOLAR LAv AGE shows increased cells (lymphocytes and granulocytes).
Although an extrinsic allergic bronchiolar alveolitis due to inhalation of the spores of Micropolyspora faeni is common among farmers, it is probably more common for these individuals to suffer from asthma related to inhalation of antigens from a variety of mites that infest stored grain and other vegetable material. The common ones are Lepidoglyphus domesticus, L. destructor and Acarus siro. Symptoms of asthma resulting from inhalation of these allergens are often mistaken for farmer’s lung. Pigeon fancier’s lung is quite common, but alveolitis from budgerigars is very rare.
Prevention is the aim. This can be achieved by change in work practice, with the use of silage for animal fodder and the drier storage of hay and grain. It is difficult to control pigeon fancier’s lung, since individuals remain addicted to their hobby.
Prednisolone, initially in large doses of 30-60 mg daily, is necessary to cause regression of the early stages of the disease. Established fibrosis will not resolve and in some patients the disease may progress inexorably to respiratory failure in spite of intensive therapy. Farmer’s lung is a recognized occupational disease in the UK and sufferers are entitled to compensation depending on their degree of disability.
Humidifier fever may present with the typical features of extrinsic allergic bronchiolar alveolitis without any radio graphic changes. This disease has occurred in outbreaks in factories in the UK, particularly in printing works. In North America it is more commonly found in office locks with contaminated air-conditioning systems. The cause remains unknown but probably involves several bacteria or even amoebae. Humidifier fever can be prevented by sterilization of the recirculating water used in the very large humidifying plants in industry.
Drug-induced lung disease
Drugs may produce a wide variety of disorders of the respiratory tract. Pulmonary infiltrates with fibrosis may result from the use of a number of cytotoxic drugs used in the treatment of cancer. The commonest cause of these reactions is bleomycin. The pulmonary damage is doserelated, occurring when the total dosage is greater than 450 mg, but will regress in some cases if the drug is stopped. The most sensitive test is a decrease in gas transfer and therefore gas transfer should be measured repeatedly during treatment with the drug. The use of corticosteroids may help resolution.
Some of the most important drugs affecting the respiratory tract are shown in Table 12.12, together with the types of reaction they produce. The list is not exhaustive; for example, over 20 different drugs are known to produce a systemic lupus erythematosus-like syndrome, sometimes complicated by pulmonary infiltrates and fibrosis. Paraquat ingestion can cause severe pulmonary oedema and death, and fibrosis develops in many of those who survive.
Irradiation of the lung during radiotherapy can cause a radiation pneumonitis. Patients complain of breathlessness and a dry cough. Radiation pneumonia results in a restrictive lung defect. Corticosteroids should be given in the acute stage.