Deafness that is present at birth (congenital deafness) or that develops over time can be hereditary, even if the deaf person’s parents are not deaf. In the majority of cases, about 75 percent, inherited deafness is due to a recessive autosomal trait in which each parent carries a recessive gene for the condition. The American Hearing Research Foundation estimates that congenital deafness occurs in 1 out of 1,000-2,000 births.
Inherited Deafness as Part of a Syndrome
In most of these cases, deafness is the main disorder, while in about 20 to 30 percent of cases, the deafness is just one of a number of disabilities caused by another disorder, per the Centers for Disease Control and Prevention. Among these other disabilities are vision disorders and additional developmental disorders, although the developmental effects may also be due to premature birth in many cases.
Unfortunately, it’s common for parents to not realize right away that their child may be deaf. If the parents know there is a risk of a genetic disorder, or if the parents do not know of a genetic disorder but suspect something is amiss with the child’s hearing, the child should undergo testing for audiological issues (with both an ENT and an audiologist) as soon as possible. An ENT and an audiologist can evaluate the child and determine whether there are additional conditions affecting the child’s development, such as speech disorders. The earlier the child can be evaluated and diagnosed, the easier it will be to provide services to help the child cope with the deafness. These services range from basic speech therapy to more involved procedures like cochlear implant surgery.
Why Recessive Genes Can Result in Real-Life Deafness
Recessive genes are those that take a backseat to dominant genes, but recessive traits can show up in a person if both parents carry the recessive gene. Each child of two parents with recessive genes has a 25 percent chance of developing the recessive trait. Autosomal dominant deafness is rarer than the recessive version, even though dominant genes are more easily expressed in offspring, according to the American Academy of Otolaryngology.