Deafness accounts for the highest proportion of many congenital disabilities.Nearly half of deaf patients are hereditary deafness. In addition, acquired deafness diseases such as drug-induced deafness and presbycusis are also closely related to genetic factors.
Hereditary deafness mainly has four inheritance modes: recessive, dominant, sex-linked chromosomal inheritance and mitochondrial maternal inheritance.Autosomal recessive inheritance is the most common form of inheritance, accounting for about 80% of hereditary deafness.The characteristic of this genetic method is that both parents can have normal hearing, but each carry a single recessive gene mutation.In offspring children, if the child inherits the two genetic mutations carried by the parents from the parents, it is very likely to cause hereditary deafness.Generally speaking, patients with deafness inherited in a recessive manner often have hearing impairment at birth, and the hearing loss is more serious, which is more common in severe and extremely severe deafness.
Autosomal dominant deafness accounts for about 15% of hereditary deafness.Contrary to recessive hereditary deafness, dominant hereditary deafness is characterized by the fact that as long as the patient carries a single dominant gene mutation, it can cause deafness. One of the patient’s parents and older ancestors often has deaf patients, and the family history is more obvious.Most deafness with dominant inheritance has mild hearing loss. Hearing conditions are usually acceptable at birth, but gradually deteriorate with age.
The proportion of sex-linked chromosome inheritance and mitochondrial maternal inheritance is relatively low, accounting for only 2% to 3% of hereditary deafness.But compared with other countries and races, the mitochondrial gene mutation A1555G is more common in the Chinese population.This mutation can cause patients to be sensitive to aminoglycoside antibiotics, which can easily lead to drug-induced deafness.Therefore, people with mutations in the mitochondrial gene A1555G should try to avoid exposure to aminoglycoside antibiotics such as gentamicin and streptomycin.This is especially important for babies who have just been born, are more susceptible to infections and often need to use antibiotics.
At present, many domestic medical units including Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine and PLA General Hospital have launched genetic diagnosis services for hereditary deafness.Genetic diagnosis of deafness helps to understand the type and composition of genetic mutations carried by patients and their families, and is particularly meaningful for the following three types of people:
The first category is hereditary deafness patients or their relatives who have a family history of deafness and face the choice of marriage and childbirth.Before officially giving birth or getting married, the above population may consider doing a common deafness gene mutation test to reduce the possibility of hereditary deafness in the offspring.Once the examination results prove that both parties carry genetic mutations that can lead to hereditary deafness, further consideration can be given to prenatal diagnosis by amniocentesis to reduce the chance of birth defects.Genetic diagnosis of deafness can effectively advance the time of prevention and treatment of deafness to prenatal or pre-pregnancy.
The second category is newborns with a family history of hereditary deafness.At present, newborn hearing screening has been widely implemented in some areas of the country, which can detect possible hearing problems in newborn babies.However, in a considerable proportion of patients with hereditary deafness, hearing loss may be delayed, progressive or sudden.These hearing impairments are not easy to be found before the child’s speech period. If they are neglected, they may cause developmental delays or obstacles to the child’s speech function, which may affect the child’s future learning and expression in severe cases.Genetic diagnosis can be used as an effective aid to hearing screening to help diagnose or predict these potential early hearing impairments, so as to ensure that these newborns are deaf but not dumb.
The third category is patients with drug-induced deafness who carry the A1555G mutation of the mitochondrial gene and are sensitive to aminoglycoside antibiotics.If the mother or maternal family members have a history of drug-induced deafness, it is recommended that such people be tested for mitochondrial gene mutations.If mutations that can cause deafness are found, the use of aminoglycoside antibiotics should be avoided as much as possible. (Author: Yang Tao Source: Health News)
