Down syndrome ( trisomy 21 ) - Causes, Symptoms and Treatment .MF .
Down syndrome (abnormality, also called trisomy 21) is a genetic disorder that occurs in about 1 in 800 newborns.It is the leading cause of cognitive impairment.Down syndrome is associated with mild to moderate developmental delay, people with the disease have characteristic facial features, poor muscle tone in infancy.Many people with Down syndrome have heart defects, increased risk of developing leukemia, early onset Alzheimer's disease, gastrointestinal disease, and other health problems.Symptoms of Down syndrome are located in a range from mild to severe degree of development.
People with Down syndrome
syndrome Down syndrome is named after Dr. Langdon Down, who in 1866 first described this syndrome as a disorder.Although the doctor described the important and fundamental symptoms, but it is not right to determine what exactly causes this pathology.It was only in 1959, scientists discovered the genetic origin of Down syndrome.Genes for additional copies of chromosome 21 are respo
Typically, each human cell contains 23 pairs of different chromosomes.Each chromosome carries the genes that are required for proper development and maintenance of the body.In concept, a person inherits 23 chromosomes from the mother (in the egg) and 23 chromosomes from the father (in the sperm).However, sometimes a person inherits an extra chromosome set from one of the parents.In the case of Down syndrome, the most common inherited two copies of chromosome 21 from the mother and one 21 th chromosome from the father, in total there are three of chromosome 21. It is because of this type of inheritance is called Down syndrome trisomy on the 21st chromosome.
About 95% of people with Down syndrome inherit an extra chromosome 21. All About 3% to 4% of people with Down syndrome do not inherit all the additional chromosome 21, and only a few extra genes from chromosome 21, which are attached to another chromosome (usually chromosome 14).This is called translocation.Translocation in most cases are random events during the time of conception.In some cases, however, one of the parents is a carrier of a balanced translocation: a parent has exactly two copies of chromosome 21, but some genes are distributed in another chromosome.If a child inherits a chromosome with extra genes of chromosome 21, then the child will have Down syndrome (two of chromosome 21, plus extra genes on chromosome 21 that is connected from the other chromosomes).
about 2% -4% of people with Down syndrome inherit additional genes of chromosome 21, but not in every cell of the body.It mosaic Down syndrome .These people can, for example, to inherit part of the chromosomal abnormalities, t. E. An additional 21-chromosome can not be in all human cells.Since people with Down syndrome mosaic number of cells varies across the range, they often will not have all the features of Down syndrome may not be as strong intellectual disturbances as people with complete chromosome 21 trisomy.Sometimes mosaic Down syndrome is so minor that it will go unnoticed.On the other hand, mosaic Down syndrome can also be incorrectly diagnosed as trisomy on chromosome 21, if there were no genetic testing done.
There is a question that scientists from around the world are working at the moment, which of the additional genes in chromosome 21 lead to the development of certain symptoms.The exact answer to this question is still there.Scientists believe that the increase in the number of specific genes alters the interaction between them.Some genes are more active than others, while others are less active than normal.As a result of this imbalance is disrupted differentiation and development of both the organism and the psycho-emotional sphere, including myself, and intellectual development.Scientists are trying to figure out which genes of the three variants of the chromosome 21 are responsible for one or another sign of Down syndrome.Currently, there are about 400 genes on chromosome 21, but the function of the majority is not clear to this day.
only known risk factor for Down syndrome is the age of the mother.The older woman at the moment of conception, the greater the risk of having a child with Down syndrome.Maternal age at conception is a risk of Down's syndrome:
25 years, 1 of 1250
30 years, 1 in 1000
35 years 1 400
40 years 1 100
45 1 of 30
Down syndrome is not a hereditary disease,although predisposition to develop it exists.Women with Down syndrome likelihood of conceiving a child patient is 50%, there is often a spontaneous abortion.Men with Down syndrome are infertile, except for the mosaic variant syndrome.In carriers of the genetic translocation of chromosomes probability of having a child with Down syndrome will also be increased.If the carrier is the mother of a child with Down syndrome are born to 10-30% if the carrier father - 5%.
Healthy parents whose child was born with Down syndrome have a 1% risk of conceiving another child with Down syndrome.
Symptoms and Signs of Down's syndrome.
Despite the severity of Down syndrome range from mild to severe, the majority of people are well-known symptoms.They include the following features:
• flattening of the face and nose, a short neck, a small mouth, sometimes with a large, protruding tongue, small ears, eyes slanting upwards, which may have a small skin folds at the inner corner;
• White spots (also known as Brushfield spots) may be present in the colored part of the eye;
• The hands are short and broad with short fingers, and with a crease in the palm;
• Weak muscle tone, developmental delay and growth.
• arcuate sky, dental anomalies, flat nasal bridge, furrowed tongue;
• Hypermobility joints, bending the chest keeled or funnel.
most common disorders associated with Down's syndrome, cognitive disorders are (communication disorders).Cognitive development is often delayed, and all people with Down syndrome have learning difficulties throughout their lives.As an extra 21th chromosome leads to cognitive impairment, it is not clear.The average size of the human brain with Down syndrome are not very different from a healthy person, but the researchers found changes in the structure and function of certain areas of the brain such as the hippocampus and the cerebellum.Especially changes the hippocampus, which is responsible for learning and memory.Scientists use human studies in animal models of Down syndrome, to find out what specific genes on chromosome 21 lead to different aspects of cognitive impairment.
addition to cognitive impairment, the most common disease associated with Down's syndrome - a congenital malformations heart.About half of all people with Down syndrome are born with a heart defect, often with atrioventricular atrial septal defect.Other common heart defects include ventricular septal defect, atrial septal defect, tetralogy of Fallot, and patent ductus arteriosus.Some cases require surgery immediately after birth to correct heart defects.
Gastrointestinal diseases are also often associated with Down syndrome, especially esophageal atresia, tracheoesophageal fistula, duodenal atresia or stenosis, Hirschsprung's disease, and non-perforated anus.People with Down syndrome have a higher risk of developing celiac disease.Corrective surgery is sometimes necessary for the gastrointestinal tract.
Some types of cancer are more common in people with Down syndrome, such as acute lymphoblastic leukemia (a type of blood cancer), myeloid leukemia, and testicular cancer.Solid tumors, on the other hand, are rare in this population.
Patients with Down syndrome have some predisposition to such conditions as: hearing loss, frequent infections of the middle ear (otitis media), thyroid pathology (hypothyroidism), cervical spine instability, visual disturbances, sleep apnea, obesity, constipation, infantile spasms, seizures, dementia and early onset of Alzheimer's disease.
About 18% to 38% of people with Down syndrome have mental or behavioral disorders, such as autism spectrum disorders, attention deficit and hyperactivity, depression, stereotyped movement disorders and obsessive-compulsive disorders.
Methods of prenatal diagnosis of Down syndrome.
Several options are not invasive screening is offered to parents.If Down syndrome is suspected in connection with the screening results, a formal diagnosis can be made before the baby is born.This gives parents time to gather information about Down syndrome before birth, and the ability to take action in case of complications.
Prenatal screening is currently represented by the test for alpha-fetoprotein (AFP) and ultrasound technique.These methods can evaluate the risk of Down's syndrome, but they can not verify it with 100%.
most widely used screening test AFP.In the period from 15th to 20th week of pregnancy, take a small blood sample from the mother and examined.AFP levels and three hormones called nekonyugirovannyyestriol, human chorionic gonadotropin, and inhibin-A is measured in a blood sample.If the AFP and hormone levels change, the Down's syndrome can be suspected but not confirmed.In addition, the normal test result does not exclude Down's syndrome.Also nuchal fold thickness measured in the neck area using ultrasound.This test is performed between 11 and 13 weeks of pregnancy.In combination with maternal age the test detects approximately 80% probability of Down syndrome.Between 18 and 22 weeks of pregnancy, you can find additional markers that can be detected in a fetus with Down syndrome: measure the length of the shoulder and the hip bone, nose size, the size of the renal pelvis, small bright spots on the heart (ultrasound signs of malformation), largethe gap between the first and second toe.
There are more accurate but invasive method of diagnosis of Down syndrome.In these methods, there is a small risk of complications such as miscarriage.
- Amniocentesis is performed between 16 and 20 weeks of pregnancy.During this procedure, a thin needle is inserted through the abdominal wall and is taken a small sample of amniotic fluid.The sample is analyzed for chromosomal abnormalities.
- Chorionic villus sampling is carried out between 11 and 12 weeks of pregnancy.It includes chorionic villus sampling and placental cells either by insertion of the needle into the abdominal wall or through a catheter into the vagina.The sample was also analyzed for chromosomal abnormalities.
- percutaneous umbilical blood sampling using a fine needle biopsy.Blood examined for chromosomal abnormalities.This procedure is usually performed after 18 weeks of pregnancy.
Treatment of Down Syndrome
At the present time the disease is incurable.Related violations are corrected only when necessary (heart defects, gastrointestinal tract ...)
How can we help children and adults with Down syndrome?Despite the genetic cause of Down syndrome, it is known that there are currently no medications.It is important to stimulate, encourage and educate children with Down syndrome from infancy.Programs for children with special needs, which are offered in many countries, are able to improve the quality of life through early intervention, including physical therapy, occupational therapy, and speech therapy can be very helpful.Like all children, children with Down syndrome need to grow and develop in a safe and supportive environment.
Forecast Down syndrome
Life expectancy for people with Down syndrome has increased dramatically over the past few decades, as the health care and social adaptation greatly improved.A person with Down syndrome will be in good health on average live 55 years or longer.
People with Down syndrome are living longer today than ever before.With full integration into society, many adults with Down syndrome are now living completely independently of each other, enjoy relationships, work, and contribute to the community.
therapists Zhumagazy EN