Investigating the Genetic Causes of Mental Retardation in Children

Investigating the Genetic Causes of Mental Retardation in Children

The birth of children with mental retardation is a heavy burden on the family and society; In addition to not playing a social role, these people have a heavy economic and psychological burden on the family and society.

The most important cause of birth defects in mentally retarded children is genetic disorders, which are caused by kinship marriages.

In general, mental retardation is the lack of intelligence that causes a person to be inadequate in performing social duties or his or her inability to acquire the skills needed to learn for that person's age.

The severity of the disorder is divided into four groups: mild, moderate, severe, and deep. The basis of this classification is intelligence testing and clinical examinations.

Prevention of mental retardation in children

The most common reasons people turn to genetic counseling centers for mental retardation are:

• People who want to know how to prevent the birth of children with mental retardation;

• People who have had a child with a mental disorder in previous pregnancies and want to prevent it from recurring;

• People who have been observed to be mentally or emotionally retarded by their relatives or spouse and are concerned about recurrence;

• Couples who intend to get married;

• Pregnant women who are concerned about the possible adverse effects on their fetus due to illness or exposure to certain substances, drugs or radiation;

• Women who become pregnant at an older age (over 35);

• Pregnant women who have been diagnosed with a pregnancy problem during pregnancy screening.

In general, moderate to severe mental retardation (IQ below 50) is seen in one percent of infants; However, this rate rises to 0.3 to 0.4 percent in childhood (due to the death of more than half of these infants due to comorbidities); In 75% of cases, the cause of the mental disorder is recognizable, and in 50% of cases, severe mental retardation has a genetic cause.

Among hereditary diseases, Fragile X Syndrome is the most common cause of mental retardation in all ages; While trisomy 21 or Down syndrome is the most common cause of mental retardation in school age.

Other causes of mental retardation include intrauterine growth retardation, poisoning, intrauterine infections, maternal malnutrition, acquired diseases, environmental factors, etc.

The role of genetic counseling in reducing the birth rate of children with mental retardation

Determining the type and cause of mental retardation in an infected person, calculating the risk of recurrence according to the cause, and finally providing useful strategies and recommendations are the main steps in genetic counseling and mental retardation.

So far, more than 450 types of mental retardation have been identified with a single gene, and in addition there are various syndromes, including mental retardation with an unknown cause.

The possibility of recurrence of mental retardation is closely related to the cause in the affected person.

For example, a child with autosomal dominant mental retardation will have a 50% chance of having a similar problem, but if the cause was bacterial meningitis, the risk of recurrence in relatives is the same in the whole community.

Therefore, the first step and the most important part of genetic counseling is to identify the type and cause of mental retardation and in hereditary cases to determine the mode of inheritance according to the genealogy.

In general, the cause of mental retardation falls into one of four groups: gene mutations, chromosomal abnormalities, environmental causes, and multifactorial disorders.

Using history, examination and drawing of pedigree and paraclinical examinations, we investigate the cause and, according to the diagnosis, take the next steps.