Heredity of allergy and asthma
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Multiple population-based family and twin studies have shown genetic predisposition in asthma and other atopic disorders, although the mode of inheritance and contributing genes are unknown. It is likely that the set of contributing genes, the mode of inheritance, and the significance of genes compared to environmental factors differ between the patient groups. In other words, in these diseases, the molecular-genetic background is more complex than the diagnostic characteristics created for clinical purposes. In multifactorial diseases, the significance of genetic factors is often measured by sibling risk (X,,b). Sibling risk is defined as the risk of a co-sibling becoming affected, if his or her sibling is already affected, divided by the risk of the population at large. For asthma, the sib values vary depending on the characteristics of the study population. In Australia, Xsib = 3.5 has been reported among adult siblings, while among 16-year-old dizygotic twins in Finland, ksib value was as high as 5 [1, 2]. Those two estimates show still a rather weak genetic effect compared with Xsib values reported in other multifactorial diseases such as kb=15 in diabetes type I, Xs;b=60 in celiac disease, or Xsib =20 in multiple sclerosis .
KeywordsCeliac Disease Susceptibility Allele Founder Population Parental Chromosome Shared Environmental Factor
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