IL13 and asthma: In general, heritability estimates for FA are as high as 81%,42 while the heritability of AR is estimated at approximately 91%.42 Twin studies reveal that about 25% of phenotypic variation in asthma severity can be explained by genetic factors; for example, RAD50- IL13 on chromosome 5q and the ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3)- gasdermin B (GSDMB) locus on chromosome 17q21 were found to be associated with asthma severity.43 Besides, the concordance rate for AD in identical twins is about 80%, which is remarkably elevated compared with the 20% found in fraternal twins.44