Heritability in general and specific atopy: A twin study

Abstract

Background: Although the genetics of overall atopy has been frequently explored, little is known about the influences of genetic factors on development of hypersensitivity to specific allergens. Objective: To study the influence of genetic and environmental factors on variation in overall atopy as well as to the susceptibility to become sensitized to specific allergens in twins. Methods: The study population was based on Danish adult twins born between 1953 and 1982 registered in the Danish Twin Registry. In total, 575 individuals participated in the study, comprising of 256 twin pairs (89 monozygotic, MZ and 167 dizygotic, DZ twin pairs) and 63 single twins. Skin prick tests were performed and for both MZ and DZ twins concordances were calculated for overall atopy, same number of positive allergens, and for reaction to the exact same allergens. Results: The study showed that the concordance for overall atopy were higher for MZ (0.68) compared to DZ (0.5) twins, p = 0.23, although not significant. The concordance for the same number of positive allergens was higher for MZ twins vs. DZ twins, 0.33 vs. 0.1, p=0.02. The concordance for reactivity to exactly the same allergens was higher, but not statistically significant in MZ vs. DZ twins, 0.12 vs. 0.02, p=0.09. MZ twins had significantly higher concordances compared to DZtwins for sensitivity to birch, ragweed and dog. Conclusion: The findings indicate an extensive influence of genetic factors on development of atopy and reactivity to specific allergens.