The general clinical manifestations of intellectual disability are varying degrees of mental retardation and poor social adaptability. So what is a first-level intellectual disability? Let me tell you what a first-level intellectual disability is. Let’s take a look! Standards for first-level intellectual disabilities

Classification standards

The intellectual disability grading standards of the World Health Organization (WHO) and the American Association on Mental Retardation (AAMD) classify intellectual disabilities according to their intelligence quotient (IQ) and social adaptive behavior.

First-level intellectual disability

That is, extremely severe intellectual disability. IQ value is 20 or below. The adaptive behavior is extremely poor; the face is obviously sluggish; the entire life needs to be taken care of by others; the motor and sensory functions are extremely poor. If trained, the patient can only respond to the movements of the lower limbs, hands and jaws. (Note: The former IQ value is measured by the Stanford-Binet scale and the latter is measured by the Wechsler scale)

Second-level intellectual disability

That is, severe intellectual disability. IQ value is between 20-25 or 25-40. Poor adaptive behavior; it is difficult to take care of oneself even after training, and still needs care from others; poor motor and language development, and poor ability to interact with others.

Level III intellectual disability

That is, moderate intellectual disability. IQ value is between 35-50 or 40-55. Incomplete adaptive behavior; incomplete practical skills, such as being able to take care of themselves partially and doing simple housework; having preliminary knowledge of health and safety, but poor reading and calculation skills; poor ability to distinguish the surrounding environment and being able to communicate with others in a simple way People interact.

Level IV intellectual disability

That is, mild intellectual disability. IQ value is between 50-70 or 55-75. Adaptive behavior is lower than the level of ordinary people; has considerable practical skills, such as being able to take care of oneself, and can undertake general housework or work, but lacks skills and creativity; generally can adapt to society under guidance; after special education, can obtain certain Reading and calculation skills; good ability to discern the surrounding environment. Able to interact with people more appropriately. Relevant definitions of intellectual disability

Intellectual disability

Our country’s definition of intellectual disability is: intelligence is significantly lower than the average person’s level and shows adaptive behavioral disorders. Intellectual disability includes: mental retardation due to various reasons during the period of intellectual development; intellectual impairment due to various reasons after intellectual development matures and dementia caused by obvious decline in intelligence in old age.

Intellectually disabled children

Intellectually disabled children refer to children whose intellectual development is lower than the average level of children of the same age during the growth and development period (before the age of 18), and who also have obvious social life adaptation. Disabled children. It can be seen that to judge whether a child has intellectual disability, we must consider three aspects: one is intelligence, the other is social adaptability, and the third is age. All three are indispensable.

Intelligence

The degree of intelligence can be expressed by IQ. The IQ of children with intellectual disabilities must be two standard deviations below the mean when taking individual intelligence tests or the percentile rank of intelligence test results must be below 3. The average intelligence level of the average person is 100, and the standard deviation of the Chinese Wechsler Children's Intelligence Scale is 15. If a child's IQ measured by this scale is lower than 70, or the IQ obtained by the intelligence test is not as good as 97 compared with children of the same age. % of children of the same age, you can suspect that this child has intellectual disability.

Social Adaptability

Judgment of children’s social adaptability depends on the Social Adaptive Behavior Test. If a child's IQ is below 70 and he has difficulty adapting to society, then the child can be considered intellectually disabled. Otherwise, even if a child's IQ is below 70 and his social adaptability is normal, the child should not be considered to be intellectually disabled. The pathogenesis of intellectual disability

1 Genetic factors

1.1 (1) Chromosome aberrations

) Chromosome aberrations include changes in number and structure. Numerical changes such as polyploidy and aneuploidy; structural changes such as chromosome breaks, deletions, duplications, inversions and translocations. Down syndrome is the most common disease caused by trisomy of the 2l autosomal pair.

Another type of chromosomal aberration in this disease is ectopy, such as G/D translocation and G/G translocation and other karyotypes. Down syndrome is a common cause of intellectual disability. Other chromosomes such as trisomy 18 and partial deletion of the short arm of chromosome 5 can cause severe mental retardation and physical deformities. Patients often die young. Prader Willi syndrome is characterized by small hands and feet, short stature, varying degrees of intellectual disability and a strong desire to eat. It is mainly caused by small deletions at chromosome 15q11~q13, and in a few families it is caused by unbalanced translocation.

Sex chromosome aberrations: For example, congenital testicular agenesis (Klinefelter syndrome) causes an extra X chromosome in males. If a woman loses one sex chromosome, she develops congenital ovarian agenesis (Turner syndrome). There are also karyotypes with XXX or XO/XXX chimeras. It is generally believed that the greater the number of sex chromosome X aberrations, the more severe the degree of intellectual disability. Chimeras generally suffer relatively mild intellectual impairment. Fragile chromosomal sites are associated with X-linked mental retardation. On the X chromosome, Xq27 and 28 appear at fragile sites, which exhibit special clinical characteristics and are combined with mild mental retardation to form a special clinical type called fragile X syndrome. This is another disease caused by autosomal changes after Down syndrome. There are currently only case reports in my country and no epidemiological data on this disease. However, Jin Ming et al. (1984) examined 70 children with intellectual disabilities for chromosomal fragility sites, and the results were 54.3% positive, distributed on chromosomes other than the X chromosome. on each group of autosomes. Li Sushui et al. (1997) examined 90 cases of intellectually disabled children with autism for fragile sites and fragile X chromosomes. The detection rates of fragile sites were 20% and 38% respectively. Fragile 1997).

1.2 (2) Inherited metabolic single-gene diseases

Single-gene genetic diseases are relatively common. It accounts for 1% of all births and causes approximately 4,000 to 5,000 human diseases. Among them, 300 species are damaged in brain function caused by abnormal biochemical metabolism. Usually, about 25% of the clinical symptoms of single-gene diseases are present at birth, and all first-level intellectual disabilities appear in early adolescence. Such as phenylketonuria and several neurocutaneous syndromes. Neurofibromatosis is a common one. The prevalence rate is 1/5000~1/4000. Phenylketonuria is a typical representative of inherited metabolic defects. Congenital deficiency of phenylpyruvate hydroxylase cannot oxidize phenylpyruvate to tyrosine, resulting in the accumulation of large amounts of phenylpyruvate, which affects the development of the central nervous system and normal physiological functions. Another example is galactosemia, which occurs because the process of converting galactose 1-phosphate into glucose 1-phosphate is blocked or lactose accumulates in the blood and tissues, causing damage to the liver, kidney, brain and other organs. In addition to the resulting physical In addition to symptoms, children also have intellectual disabilities.

2 Environmental factors

The broad environmental factors include:

2.1 (1) Harmful factors during pregnancy and childbirth

Estimated pregnancy risk , The impact of harmful factors during childbirth on intellectual disability accounts for 10% to 20% of the total, while postpartum injuries account for about 5% to 10%. The main harmful factor during pregnancy is infection, especially infection in early pregnancy. For example, 15% to 20% of babies born to pregnant women infected with cytomegalovirus and herpes simplex virus in the first 3 months of pregnancy will have congenital malformations. The incidence rate of the former is about 1/3000. Manifested as microcephaly, mental retardation, hydrocephalus and epilepsy. Another thing worth noting is toxoplasmosis and protozoa, which are mostly infected by pregnant women coming into contact with animals. The impact of harmful physical and chemical substances on the fetus also often occurs in early pregnancy. For example, improper use of drugs, radiation, heavy metals such as mercury and lead caused by industrial pollution and excessive water and air quality may cause damage to the normal development of the fetus. Alcohol and nutritional problems are also another important harmful factor (Nico Bkichrodt, 1989; Yang Xiaoling, 1999). About 10% to 15% of babies born to mothers who are chronic alcoholics have fetal alcohol syndrome. Clinical symptoms include growth failure, facial deformities, cognitive impairment, intellectual disability, sometimes accompanied by limb and skeletal abnormalities, and often attention deficit disorder.

In some areas, iodine deficiency can cause severe mental retardation.

Lead contamination in gasoline and paints and coatings is also serious in some areas and may cause effects on the fetus. Studies have shown that cognitive and behavioral disorders may occur when blood lead levels are 10 to 25 U/dl. In the mid-1980s, nearly 10% of American preschool children had blood lead levels of 20 U/dl, while about 20% of children in low-income families had blood lead levels of 30 U/dl. Therefore, in countries with urban industrial development, it is a harmful factor that cannot be ignored.

The health of women during pregnancy directly affects the normal development of the fetus. Serious chronic diseases, such as heart disease, diabetes, hypertension, chronic kidney disease and severe anemia, can cause fetal ischemia and hypoxia, leading to immature infants, intrauterine growth retardation, low birth weight infants or nervous system damage, and intrauterine asphyxia. and intracranial hemorrhage. The impact of maternal diseases on the fetus during pregnancy accounts for about 6% of newborns, and about 1/5 of them are serious. Signs of poor prognosis in the neonatal period include an Apgar score below 6 or 7 and early onset convulsions.

2.2 (2) Harmful factors in newborns and infants and young children

It is estimated that 5% to 10% of intellectual disabilities are related to such factors. Including severe poisoning, infection, hypoxia, trauma, malnutrition and psychosocial factors in newborns and infants and young children, such as Japanese encephalitis. Toxic encephalopathy caused by various infections, hemolysis caused by various reasons, increased bilirubin, Rh factor hemolysis, hemolysis caused by drugs, hypoxia caused by various reasons, such as severe convulsions, severe congenital heart disease, etc.