Overview of common chromosomal abnormalities (Down syndrome, Edward syndrome, and Patau syndrome)

Overview of common chromosomal abnormalities (Down syndrome, Edward syndrome, and Patau syndrome)

Down syndrome or trisomy 21

There is a strong link between Down syndrome and increasing maternal age. Clinical signs of hypotonic birth include drooping eyelid grooves, small ears, and protruding tongue.

 There are also wrinkles around the eyes, spots and white spots on the iris and earthenware braces. In 50% of them, a palm groove is seen. Clinodactyly (tilting of the fifth finger), congenital heart disease (45-40%) with ventricular and atrial wall defects and arterial duct obstruction are other obvious symptoms of these patients.

IQ is between 75 and 25. Patients who do not have heart disease survive to the age of 50-60, and the rest die prematurely. Most adult patients develop Alzheimer's disease, which is caused by the prognostic gene dose of the amyloid protein precursor on chromosome 21.

Down syndrome can be seen in the following four forms:

1- In 95% of cases, trisomy 21 chromosome is present, in more than 90% of them, the extra chromosome is of maternal origin and occurs due to non-differentiation in maternal meiosis I.

2. Robert Sonin's move is 4%.

3. Children with mosaicism have a small ratio (1%)

4 - and in rare cases, parietal trisomy 21 (ie only a small part of chromosome 21 is repeated) is seen.

The critical area is affected (Down Syndrome Critical Region, 21q22.1).

Chromosome 21 is genetically poor (high AT / GC ratio). Recurrence of trisomy 21 depends on the mother's age and usually ranges from 1: 100 to 1: 200.

In cases of familial displacement, the risk is 1-0.3% for men and 10-15% for women. With the exception of rare carriers, the q 21 displacement is 21%, which is a 10% chance of recurrence.

 Prenatal diagnosis is made by CVS or examination of amniotic cells (obtained during the amniocentesis process).

Patau syndrome (trisomy 13) and Edward syndrome (trisomy 18)

Both occur in 1 in 5,000 and have a poor prognosis.

Affected babies die in the first days and weeks of life. Heart abnormalities are seen in 90% of cases.

These syndromes are associated with maternal age, and the extra chromosome is of maternal origin.

 10% of cases are due to mosaicism or unbalanced layout (especially Robert Sonin's shift in the case of Pato).

Patau syndrome is associated with cleft lip and palate.

Trisomy 18 or Edward's syndrome is recurrent and has tied hands.