Trisomy 18 is also called Edwards syndrome and occurs in about 1 out of every 3000 live births. Unlike Down syndrome, Trisomy 18 is usually fatal, with most of the babies dying before birth. Those babies who do make it to birth typically live only a few days. However, a small number of babies (At conception, 23 chromosomes from the father and 23 chromosomes from the mother combine to create a baby with 46 chromosomes in each cell, two of each type. Each chromosome holds a particular “position” in the cell and carries certain genetic material. A trisomy occurs when a baby has three chromosomes in one position instead of the normal two.
The most common trisomy is Trisomy 21, also known as Down Syndrome, where a baby has three of the twenty-first chromosome. Trisomy 18 is the second most common trisomy and occurs when a baby has three of the eighteenth chromosome. This results in 47 chromosomes instead of the normal 46 in the affected cells. It is this extra genetic material that causes the problems associated with Trisomy 18.
Symptoms may include:
- Clenched hands
- Crossed legs (preferred position)
- Heart defects (congenital)
- Hole, split, or cleft in the iris (coloboma)
- Kidney problems
- Low birth weight
- Low-set ears
- Mental deficiency
- Separation between the left and right side of the rectus abdominis muscle (diastasis recti)
- Small head (microcephaly)
- Small jaw (micrognathia)
- Umbilical hernia or inguinal hernia
- Underdeveloped fingernails
- Undescended testicle
- Unusual shaped chest (Pectus carinatum)
- Omphalocele (a portion of the intestinal tract is located outside the stomach in a sac
- Esophageal atresia (the esophagus does not connect to the stomach, meaning the baby cannot eat by mouth)
Signs and tests
Examination of the pregnant woman may show an unusually large uterus and extra amniotic fluid. An unusually small placenta may be seen when the baby is born.
Physical examination of the infant may show unusual finger print patterns. X-rays may show a short breast bone. Chromosome studies show trisomy 18, partial trisomy, or translocation.
There are often signs of congenital heart defects, such as:
- VSD (ventricular septal defect)
- ASD (atrial septal defect)
- PDA (patent ductus arteriosus)
- Coarctation of the Aorta
Tests may also show kidney problems, including:
- Horseshoe kidney
- Hydronephrosis (swelling of kidneys)
- Polycystic kidney (enlarged kidneys due to cysts)
Treatment
Medical management of children with Trisomy 18 is planned on a case-by-case basis and depends on the individual circumstances of the patient.
Source: Trisomy18.org
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