Coincidence of atopy and its profile (monosensitization/polysensitization) between sibling pairs

Background: Results of epidemiologic studies have shown that childhood atopy is probably a hereditary disorder. In the atopic population, some individuals are sensitized to only 1 class of allergens (monosensitized), whereas others are sensitized to more than 1 class of allergens (polysensitized). Objective: To investigate whether atopy and its profile (monosensitization/polysensitization) tend to coincide in sibling pairs. Methods: We evaluated sensitization to 5 classes of aeroallergens (house dust mites, animal danders, pollens, molds, and cockroach) using skin prick testing in 564 children with symptoms suggestive of allergic diseases (index children) and their paired siblings. Results: The frequency of sibling atopy was highest (56.8%) for polysensitized index children (n = 222), intermediate (45.4%) for monosensitized index children (n = 196), and lowest (30.8%) for nonsensitized index children (n = 146). The proportion of polysensitization among atopic siblings was significantly higher for polysensitized (47.6%) than for monosensitized (32.6%) index children. Polysensitized index children were found to more frequently have polysensitized siblings (27.0%) than were monosensitized index children (14.8%), with an odds ratio of 2.13 (95% confidence interval, 1.30-3.49), whereas the likelihood of having a monosensitized sibling was similar for monosensitized and polysensitized index children. Conclusion: These data suggest a coincidence of atopy and its profile in terms of monosensitization and polysensitization in sibling pairs, although the relative importance of genetic and environmental influences requires further study.