Recessive Inheritance

In recessively inherited EB, both parents carry an abnormality or mutation in the same gene. But because recessive traits and disorders require two copies of the gene for the trait or disorder to be present, neither of the parents has EB. Instead, the parents are carriers of this abnormal gene. In these parents, the second copy of the gene is normal. In order for EB to occur in their children, both parents must pass the mutated copy of the gene to the child. When two copies of the abnormal gene are paired, recessively inherited EB occurs. If only one parent passes the abnormal gene to the child, then the child will be a carrier but will not have EB. With recessive inheritance, there is a 25 percent chance with each pregnancy that the child will have the disorder. An individual with a recessive form of EB will be at risk of having an affected child only if he or she has a child with a carrier or another person with recessive EB.