Is allergenic similarity predictable in respiratory allergies?

BACKGROUND First degree relatives of patients with allergic diseases are at increased risk of having the disorder. However, it is not clear whether two such related patients with allergic diseases are sensitive to the same antigens or not. OBJECTIVE The aim of this study to determine whether or not first degree relatives with respiratory allergies are more likely to be skin test positive to the same allergen extracts as unrelated patients. PATIENTS AND METHODS Skin test results for 35 common aeroallergens were compared in 264 pairs of genetically related subjects and 264 pairs of age and sex matched, but unrelated, subjects. We calculate the percentages of the concordant and discordant results in each group. Results are compared by using chi2 test. RESULTS For all related and unrelated groups combined, there were significant differences with mites (der. pteronyssinus, der. farinae) and some moulds (aspergillus mix and rhizopus nigricans) (p<0.05); When the groups were subdivided into parent-child pairs and same or different sibling pairs, and the same comparisons were made, a significant difference was only found in both sibling pairs (p<0.05), not in parent-child pairs (p>0.05). Since there was no both positivity with aspergillus mix and rhizopus nigricans in the two groups, these two allergens were excluded from the study. CONCLUSION It is concluded that we could not say that if one or both of parents are atopic to any allergens, their child will be atopic to the same allergens. Besides, when a respiratory allergy occurs in siblings, only the one who has house dust mite allergy sensitivity can possess the similar antigen sensitivity.