Down’s syndrome is a chromosomal disease caused by trisomy of chromosome 21, usually due to a violation of chromosome segregation during meiosis of the egg. Frequency – 1 per 650 live births (the overall frequency in the population is higher, given that over 2/3 of the affected fetuses die in utero). The frequency increases with maternal age, which is confirmed by amniocentesis data (especially sharply after 30 years). Genetic aspects (see also Appendix 2. Hereditary diseases: mapped phenotypes)
- Trisomy 21: 90-95% of patients have an extra 21 chromosome in all cells
- Unbalanced translocation 21: in 5% of patients, the long arm of chromosome 21 is translocated to another chromosome, usually to 14. Among translocation trisomies, 1/2 are newly arisen, 1/2 is a consequence of a balanced translocation in one of the parents
- Mosaic trisomy 21: 1-5% of patients have 2 or more cell populations: usually normal and trisomy 21 (clinical manifestations are traditionally less pronounced). Pathomorphology. After 20 years, plaques characteristic of Alzheimer’s disease are found in 100% of patients in the brain.
- Newborns and children
- Brachycephaly (100%)
- Mongoloid eye section (90%)
- Epicanthus (90%)
- Macroglossia (75%)
- Brushfield spots on the iris (50%)
- Ear anomalies
- convergent strabismus
- Wide nose bridge
- small chin
- short neck
- UPU (up to 30% of babies)
- Four-finger palmar crease
- Absence of plantar curls (balls of the toes)
- Convergence (up to merging) 2-3 flexion folds of the little finger
- Stenosis or atresia of the duodenum
- No anus
- Hirschsprung disease in 2-3% of babies
- Delayed psychomotor development (may not appear until 1 year of age)
- Increased susceptibility to infections.
- Adults. Most manifestations are milder, brachycephaly is preserved. In patients, a delay in cognitive function is noted (IQ – 40-45), although individuality and sociability are preserved. After the age of 35, dementia develops, similar to Alzheimer’s disease. Most patients are capable of self-care. Some have jobs, although they require guardianship. In some patients, autistic tendencies are observed, a small percentage of patients are non-verbal. Males are always infertile (no spermatogenesis).
- The study of the chromosome set (karyotype) will always be necessary to exclude translocations
- Given the frequent combination with leukemia – hematological studies annually
- Determination of the level of thyroid hormones (hypo-, hyperthyroidism) is shown
- In infants with pyuria and unexplained fever, abdominal ultrasonography for urinary tract abnormalities
- All babies have
- echocardiography (ventricular septal defect may
not present at birth).
- Excessive neck fold (16-29 weeks of gestation)
- Increase in the anteroposterior size of the collar space (10-14 weeks of gestation)
- Moderate ventriculomegaly
- hyperechoic intestine
- duodenal atresia
- Non-immune fetal dropsy
- Moderate hydronephrosis
- limb shortening
- Hypoplasia of the middle phalanx of the little finger
- Biochemical parameters of mother’s serum
- Decrease in serum AFP less than 50%
- Increased levels of HCG and unconjugated estriol. differential diagnosis. Trisomy 22 and deletion of the short arm of chromosome 9 may clinically resemble Down’s syndrome, which requires a mandatory karyotype study.
Tactics of conducting
- Genetic research and consultation
- CCC research. Surgery. WPS correction.
- Bowel obstruction (fistulas, intestinal tube abnormalities in 10% of cases)
- Thyroid diseases (hypo- and hyperthyroidism in 5-8%)
- Leukemia (0.5%)
- Alzheimer’s disease in older age.
Current and forecast. The outcome and duration of the disease largely depend on the presence of CHD. Life expectancy is reduced: 30% die in the first year of life, 50% do not live past age 5, and only 8% survive beyond 40 years. In 1/3 patients in the first year of life, the development is within the normal range, in the subsequent
- slight deviations (slowdown of development after the first year of life, moderate deviations of speech and cognitive functions). Gastrointestinal complications and heart failure in CHD may begin suddenly. Hypothyroidism appears, as a rule, 6 months after birth, a typical symptom is growth retardation. age features. In 1/3 of patients older than 35 years, clinical manifestations of Alzheimer’s disease are observed,
- Prenatal karyotyping in women at risk
- Low maternal serum AFP at 14-16 weeks of gestation (helps to identify 1/3 of cases).
- Trisomy 21
- Trisomy G ICD. Q90 Down’s syndrome MSH. 190685 Down syndrome
Note. The term mongolism was previously used to refer to the disease. Mongoloid idiocy.