Clinical aspects of farmer's lung: airway reactivity, treatment and prognosis.

This study reviews the results of five clinical studies dealing with farmer's lung (FL). The total number of patients included was 107, with a mean age of 49 years. All patients were farmers with dairy cattle. The clinical symptoms, auscultatory findings, chest radiography, laboratory data, partial pressure of oxygen in arterial blood at rest (PaO2), dynamic spirometry (FVC and FEV1) and lung diffusing capacity of carbon monoxide (DLco) were recorded at the first visit to the hospital and one, three, six and twelve months later during the follow-up and every six months after that. Half of the patients with FL reported insidious onset of the disease, and 28% reported acute onset. Dyspnoea was reported by all patients, coughing was almost as common. A considerable proportion of the patients reported muscle and joint pains. Diffuse opacities were detected in the chest radiograms of 99 patients (93%): the more severe the radiological change, the more impaired the DLco value. A normal chest radiogram was seen in eight of the 107 patients at the first evaluation. Half of the patients showed a restrictive type of impairment of ventilatory function at the first evaluation. Lung diffusing capacity was less than 80% of the predicted value in 89% of the patients. Ninety-nine patients were initially challenged with histamine and twenty-two of them (22%) showed increased bronchial responsiveness. Bronchial hyper-reactivity was transient in most of the patients and might also fluctuate with exacerbation of FL symptoms. Specimens of the airway epithelium of FL patients were taken by rigid bronchoscope from five patients for electronmicroscope studies. Extensive bronchial damage to the airway epithelium associated with the presence of spore-like fungi was observed. Aspiration biopsy of the spleen was carried out on ten FL patients during their first visit to the hospital. Granuloma-like reactions were detected in the aspiration biopsy material of five FL patients. The granulomatous changes in the spleen had disappeared when the procedure was repeated on two patients at an asymptomatic stage of the disease. Ninety-three patients were included in a follow-up study with a mean follow-up period of 18.6 months. The patients with clinically less severe disease were observed without medication. It appeared that corticosteroid medication was usually started if the DLco value was less than 65% of the predicted value. Fourteen patients with a DLco value less than 65% were observed without medication and served as a control group for those on medication.(ABSTRACT TRUNCATED AT 400 WORDS)