The changes in clinical features and pathogenesis of intractable asthma over two decades were clarified in this study. There has been an increase in older intractable asthmatics, the age of onset has advanced, and the duration of asthma has become shorter compared with 20 years ago.
Intractable asthmatics were classified into 16 types according to the 4 factors of allergy, aspirin sensitivity, heredity, and respiratory infection. The clinical features of 57 cases of intractable asthma were studied with respect to the 4 factor groups and their classification. The result showed that respiratory infection occurred more often in intractable asthma than in non-intractable asthma, and that fewer cases of intractable asthma have allergy compared with non-intractable asthma.
MAST for 26 allergens showed that the positive ratio in intractable asthma was lower than it in non-intractable asthma. Chest X ray photographs, CT scan photographs and complications were examined in intractable asthma. Many organic abnormalities in the lung and complications such as diabetes mellitus were often observed, and such abnormalities induced respiratory infections with consequent asthmatic attacks in the intractable asthmatic patients. Thus infectious factor occurs predominantly in their classification.