Abstract

A further example of diffuse pulmonary hypersensitivity to an inhaled organic antigen is reported. A 42-year-old maltworker, who developed an illness resembling farmer's lung, was found to have been heavily exposed to the spores of Aspergillus clavatus. Precipitating and complement-fixing antibodies against an extract of A. clavatus were detected in his serum, a late (Arthus-type) reaction was produced by intradermal injection of the same extract, and a pyrexial reaction, accompanied by a reduction in forced vital capacity and carbon monoxide transfer factor, occurred 6 hours after the inhalation of spores of A. clavatus. Two of the patient's four workmates complained of similar but less severe symptoms, and their sera also contained specific antibodies. Although the spores of A. clavatus and of Cryptostroma corticale, the fungus responsible for maple-bark disease, are much larger than the 1 μ spores of Micropolyspora sp., they may give rise to a diffuse pulmonary hypersensitivity reaction indistinguishable from that observed in farmer's lung. This suggests that the occurrence of such a reaction is not necessarily related to the size of the inhaled particles, and there is reason to believe that the concentration of spores or other antigenic particles in the inspired air may in this respect be more important than their size. The pulmonary hypersensitivity in this group of disorders appears to be a precipitin-mediated (type III) response to a variety of inhaled antigens, but some of these antigens may in certain patients, presumably atopic individuals, also provoke a reagin-mediated (type I) bronchial hypersensitivity reaction. It is suggested that a term such as `allergic alveolitis' or `extrinsic allergic alveolitis' may suitably be used to describe the group of diseases caused by pulmonary hypersensitivity to inhaled organic antigens.