Abstract
For the purpose of studying a possible genetic marker for asthma, IgE levels and methacholine inhalation challenge responses were studied in 45 pairs of monozygous (MZ) twins and 28 pairs of dizygous (DZ) twins. The population under study was ascertained on the basis of living within a 300 mile radius of Omaha and being between ages 6 to 30. The zygosity was determined using a questionnaire, morphological markers, and 9 blood genetic markers including HLA. History of asthma, hay fever, or atopic eczema showed that 40.0% of the MZ twins were concordant for these diseases and 8.9% were discordant, while 17.9% of the DZ twins were concordant and discordant each. A x2 analysis of the distribution showed that there was a significant increase in the concordance for asthma, hay fever, and atopic eczema among the MZ twins when compared with DZ twins (p0.05) in DZ twins. The results on the methacholine inhalation response as measured by the area under a dose response curve showed a correlation coefficient of 0.73 (p