Japanese summer-type hypersensitivity pneumonitis. Geographic distribution, home environment, and clinical characteristics of 621 cases.

A survey of hypersensitivity pneumonitis in Japan was carried out by nationwide questionnaire. A total of 835 cases of hypersensitivity pneumonitis was recognized during the last decade from 1980 to 1989. Of the 835 cases, 621 (74.4%) were summer-type hypersensitivity pneumonitis. The number of cases diagnosed doubled in the latter half of the 10-yr period. The residence of the patients was mostly in the western and southern parts of the country; the northernmost incidence was in Akita Prefecture at a latitude of 40 degrees north. Of the patients 86% experienced initial symptoms from June to September with a peak in July. Female patients were 2.0 times as numerous as male patients, probably as a result of more exposure to the offending antigen at home since 39.8% of the patients were female homemakers without an outside occupation. The frequency of family occurrence was 23.8%. The mean age of the patients' houses was 20.5 yr after building, and more than half had unsanitary conditions, such as shady, damp, or poorly ventilated rooms. Serum anti-Trichosporon cutaneum antibody activities were positive in 260 (99.2%) of the 262 cases examined. We conclude that summer-type hypersensitivity pneumonitis occupies the majority of hypersensitivity pneumonitis in the country and that to prevent the disease concentrated attention should be given to the home environment from the viewpoint of environmental medicine.