Bronchial response to methacholine inhalation challenge in families with and without asthma

This study included 140 subjects; 20 asthmatic patients, 60 as first degree relative to asthmatics and 60 from non-asthmatic families. The results showed that all asthmatic patients were highly responders to methacholine inhalation challenge with a PD20 FEV1 less than 600 ug. The responders in asthmatic families were seven cases, but in non- asthmatics families, only three cases responded to methacholine inhalation challenge. This indicated that bronchial hyperresponse to methacholine is not due to environmental factor alone, but a combination of both environmental and genetic factors are responsible for bronchial hyperreactivity