Bronchial reactivity and atopy in asthma discordant monozygotic twins.

Bronchial reactivity was studied in six asthma-discordant monozygotic twin pairs. In four pairs, atopy was confirmed in the asthmatic twin. It was not confirmed in any of the nonasthmatics. In five pairs, the asthmatic twin was markedly more reactive than the nonasthmatic partner. Bronchial reactivity correlated significantly with total IgE. The results indicate that hyperreactivity and atopy were acquired.