What happens at the chromosome level
Normally, each human cell contains 46 chromosomes - 23 pairs. In Down syndrome, chromosome 21 is present in three copies rather than two, which is why the condition is called trisomy 21. Additional genetic material influences the development of many body systems, primarily the nervous, cardiovascular and endocrine systems. At the same time, the set of manifestations varies greatly among different people, and it is impossible to predict in advance what a particular child will be like - just as it is impossible for any other child.
- Complete trisomy - approximately 95 percent of cases: an extra chromosome is present in all cells, occurs randomly
- Translocation form - about 3-4 percent: a section of the 21st chromosome is attached to another chromosome. In approximately a quarter of such cases, one of the parents is a carrier of a balanced rearrangement, so parents are recommended to have a karyotype study
- Mosaic form - 1-2 percent: the extra chromosome is present only in part of the cells, manifestations are usually milder
- Common features: reduced muscle tone in an infant, facial structural features, delayed development of motor and speech skills, varying degrees of intellectual characteristics
- The range of possibilities is very wide: some people need constant support, others graduate from college, work and live independently
Why does this happen and why is it no one's fault?
An extra chromosome appears due to chromosome nondisjunction during cell division. It is a random event that occurs before or at the moment of conception. It is not related to the parents' lifestyle, diet, past illnesses, medications, stress, work, or anything that could be prevented. It is important for parents who are looking for a reason within themselves to hear this directly: it was impossible to do anything differently.
- The likelihood of chromosome nondisjunction increases with maternal age, especially after 35 years
- Moreover, the majority of children with Down syndrome are born to women under 35 years of age - simply because the majority of children in general are born at this age
- Father's age is of lesser but significant importance
- The syndrome occurs in all countries, cultures and social groups with approximately the same frequency
- With complete trisomy, the likelihood of recurrence in the next pregnancy is low, but is discussed individually with a geneticist
- With the translocation form, the prognosis for subsequent pregnancies depends on the results of karyotyping of the parents
Screening during pregnancy: what it shows and what it doesn’t show
The key thing to understand about prenatal screening is that it calculates a probability, not a diagnosis. The result “risk of 1 in 150” means that out of 150 women with the same indicators, one will have a child with Down syndrome, and 149 will not. This is a reason for consultation with a geneticist and additional examination, and not a basis for hasty decisions. Unfortunately, it is at this stage that families most often experience severe stress due to misinterpretation of numbers.
- Скрининг первого триместра проводится в срок 11 недель — 13 недель и 6 дней и состоит of двух частей.
- Ультразвуковая часть: измеряется толщина воротникового пространства, оценивается наличие носовой кости и ряд других признаков. Это делает специалист с соответствующей подготовкой, потому что точность измерения критична.
- Биохимическая часть: анализ крови матери на два белка — связанный с беременностью протеин и свободную субъединицу хорионического гонадотропина.
- Специальная программа объединяет данные ультразвука, биохимии, возраста и срока беременности и рассчитывает индивидуальную вероятность.
- Неинвазивный пренатальный тест (НИПТ) выполняется с 10-й недели: в крови матери исследуют внеклеточную ДНК плода. Его точность в отношении трисомии 21 очень высока, но это по-прежнему скрининг, а не диагноз.
- При высоком расчётном риске женщину направляют на консультацию генетика для обсуждения подтверждающей диагностики.
Confirmatory diagnostics
An accurate diagnosis before the birth of a child can be made only in one way - by examining the fetal cells. To obtain them, invasive procedures are performed under ultrasound guidance. They carry a small risk of complications, so they are not prescribed to everyone, but after consultation with a geneticist and for specific indications.
- Chorionic villus biopsy - performed at approximately 11-14 weeks, results are obtained earlier
- Amniocentesis - sampling of amniotic fluid, usually from the 16th week
- In both cases, karyotyping is performed - a study of the complete set of fetal chromosomes; molecular methods with faster response are also used
- The risk of complications from the procedure is small, but exists, and the doctor must discuss it before making a decision
- After birth, the diagnosis is confirmed by testing the child’s blood for karyotype, which is also important for determining the form of the syndrome.
- In the translocation form, the karyotype of both parents is additionally examined
The decision to carry out invasive diagnostics is made only by the woman herself and her family, after a full and calm explanation. The doctor's task is to give information and time, and not to push to any choice.
Health: what is monitored and when
Down syndrome itself has no cure because it is not a disease. But the accompanying conditions that occur more often with it are quite treatable - and it is regular monitoring on a clear schedule that determines how healthy and active a person will be. Much of the above occurs without noticeable complaints, so checks are carried out as planned, and not based on symptoms.
- Heart: Congenital defects occur in about half of children. Echocardiography is mandatory for a newborn, regardless of the presence of murmur. Most defects can be successfully operated on in the first year of life
- Thyroid gland: hypothyroidism develops frequently and at any age, and its symptoms can easily be attributed to the syndrome itself. Thyroid stimulating hormone testing is done during the newborn period and then regularly throughout life.
- Hearing: Hearing loss occurs in a significant proportion of children, often due to fluid in the middle ear. Hearing testing is mandatory from birth onwards, because speech development directly depends on hearing
- Vision: strabismus, astigmatism, farsightedness, cataracts; examination by an ophthalmologist begins in the first year of life and continues regularly
- Gastrointestinal tract: duodenal atresia and Hirschsprung's disease appear in the first days of life; Celiac disease may occur later
- Sleep: obstructive sleep apnea is very common, snoring and restless sleep require evaluation
- Cervical spine: instability of the upper vertebrae requires attention before playing certain sports and before anesthesia
- Blood: the risk of some forms of leukemia is increased, and treatment results in such children are good; Pallor, bruises, prolonged fever should alert you
- Adulthood: Monitoring weight, thyroid, bone health and memory
Early help, development and the words we choose
Early help is a system of activities and support that begins in the first months of life, and not when the child “grows up.” Its effect has been well studied: children who have received such help from infancy begin to sit, walk and talk earlier, master self-care better and subsequently achieve greater independence. Reduced muscle tone, characteristic of infants with Down syndrome, can be corrected, but requires systematic work.
It is important that early help is addressed not only to the child, but to the entire family. The first weeks after the diagnosis becomes known are often the most difficult: parents are faced with medical information, other people's opinions, and their own fears for the future. Support from specialists and communication with families who have walked this path before mean as much here as classes. Practice shows that confusion is usually associated not with the syndrome itself, but with a lack of clear information about what to do in the coming months - and this problem can be solved.
- Physical therapy and work with motor development - from the first months, with training for parents in daily activities
- Development of communication and speech: speech understanding in children with Down syndrome usually precedes pronunciation, so gestures and pictures are introduced early as a support, not a replacement for speech
- Occupational therapy and self-care skills - eating, dressing, fine motor skills
- Regular classes at home are more important than rare intensive courses: being systematic works
- Inclusive education and peer interactions have a significant impact on social skills
- Adolescence and adulthood: vocational training, supported employment, varying degrees of independent living
And last but not least - language. It is customary to say “a person with Down syndrome”, “a child with Down syndrome”: first the person, then the feature. The words “sick”, “suffers from a syndrome”, “down” are incorrect and offensive, and “defect” and “deviation” do not describe a person, but someone’s assessment. This is not a matter of formal politeness: the words society uses to describe people directly affects the opportunities they are given - at school, in the clinic, at work. Families faced with a diagnosis notice a difference in attitude very quickly.
