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how to diagnose and differentiate chromosome abnormality-chromosome abnormality is

how to diagnose and differentiate chromosome abnormality-chromosome abnormality is

Differential diagnosis of chromosome abnormality

I. Identification

The diagnosis of chromosome abnormality includes routine chromosome analysis (chorionic or amniotic fluid cells, blood, other somatic cells or germ cells), high-resolution chromosome analysis, fluorescence in situ heterosis (FISH) and molecular genetic analysis (PCRSouthernblot).

Trisomy 21 syndrome (Down syndrome)

1. The ultrasonographic manifestations of ultrasound diagnosis mainly include:

(1) Thickening of transparent layer of neck (≥ 2.5 mm at 10-14 weeks of pregnancy and > 5mm at 18-22 weeks of pregnancy);

(2) Cervical hygroma, fetal edema and pleural effusion;

(3) Mild ventricular dilatation, the width of posterior horn of lateral ventricle ≥ 10 mm;

(4) Cardiac malformations (including atrioventricular channel, ventricular septal defect, atrial septal defect, tetralogy of Fallot, coarctation of aorta, etc.);

(5) Gastrointestinal malformation (duodenal stenosis or atresia, esophageal atresia, small intestine stenosis or atresia, etc.);

(6) Intestinal strong echo is a very special sonographic manifestation of trisomy 21 syndrome (when the gray scale gain is adjusted to show only the strong echo of bones, it is compared with the strong echo of intestine, if it is displayed at the same time, it is this phenomenon);

(7) There may be omphalocele or mild dilatation of renal pelvis;

(8) There may be short femur, clubfoot, missing or dysplasia of the second phalanx of the little finger, and bending of the little finger.

2. Differential diagnosis:

(1) Mild ventricular dilatation should be different from early hydrocephalus; Mild dilatation of renal pelvis should be different from stenosis of renal pelvis and ureter junction; Short femur should be different from intrauterine growth retardation.

(2) Although it is difficult to distinguish the clinical manifestations of Down syndrome caused by trisomy 21 from those caused by chromosome translocation, there is a strong correlation between them, which is related to the mother's age. Mothers of children with trisomy 21 usually give birth at an older age, but the incidence of chromosome translocation in older or younger pregnant women is lower. Down syndrome subtypes, such as chimeric type, have normal chromosomes in some cells and abnormal chromosomes in others. Chimeric patients may have typical manifestations of Down syndrome, but some patients have normal intelligence.

Trisomy 18 syndrome

1. The ultrasonographic manifestations of ultrasound diagnosis mainly include:

(1) Strawberry head: On the plane of fetal biparietal diameter, bilateral frontal bones are slightly invaginated, occipital frontal diameter is short, and the head shape is grass-shaped;

(2) Choroidal cyst, which may be unilateral or bilateral multiple;

(3) Thickening of cervical transparent layer or cervical hygroma and fetal edema;

(4) Cleft lip or cleft lip and palate with short mandible;

(5) Cardiac malformation (ventricular septal defect, atrial septal defect, right ventricular double flow, left heart dysplasia, etc.);

(6) Diaphragmatic hernia and omphalocele;

(7) There may be esophageal atresia, horseshoe kidney, urethral stricture or atresia, radius loss or dysplasia, finger overlap, hand deformity, second phalanx loss or dysplasia of little finger, clubfoot, single umbilical artery, fetal intrauterine growth retardation and polyhydramnios or oligohydramnios.

Trisomy 13 syndrome

1. The ultrasonographic manifestations of ultrasound diagnosis mainly include:

(1) Microcephaly, complete forebrain, loss of corpus callosum and hydrocephalus;

(2) Facial changes (such as short orbital spacing, central cleft lip, etc.);

(3) Extremity abnormality, with multi-digit toe being the most common;

(4) Cardiac malformation (ventricular septal defect, atrial septal defect, valve stenosis or atresia, abnormal venous return, etc.);

(5) Urinary tract malformation (such as cystic renal dysplasia, duplicate kidney, etc.);

(6) Omphalocele;

(7) Intrauterine growth retardation.

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