What Is Trisomy 18 / The Edwards Syndrome?

2:48 AM

The second most common autosomal trisomy, after Down syndrome is Edwards syndrome, or Trisomy 18.However, unlike Down syndrome, Trisomy 18 is more life threatening in the early months and years of life.

Trisomy 18 Foundation points out that "parents have done nothing before or during pregnancy to cause this disorder in their child".

The genetic disorder is caused by a third copy of 18 chromosome instead of just two. As a result the baby will have 47 chromosomes, instead of 46 in all the affected cells.

There are three types of Trisomy 18.

The Full Trisomy 18 is the most common type and occurs in about 95 percent of all cases. This means that the additional chromosome can be found in all the baby's cells. It is also important to know that this type of trisomy 18 isn't hereditary.

The second type is known as Partial Trisomy 18 and occurs very rare. It implies that only part of an extra chromosime is present. Certain cases of Partial Trisomy 18 may be hereditary.

The third and last type is very rare. The Mosaic Trisomy 18 develops when the extra chromosome is present only in some cells of the body.

According to Victoria Miller, executive director of the Trisomy 18 Foundation, the condition is a common  genetic disorder found in one in 3,000 births. Also, most babies die soon after birth or within a year after, however as Miller puts it, “every child is different".

Dr. Robert Marion, Chief of Genetics and Developmental Medicine at Children’s Hospital at Montefiore and Albert Einstein College of Medicine, told ABC News that “most children with Trisomy 18 die in the first three months of life, and only 10 to 20 percent survive pas the first year”.

“Those who survive are almost always girls. The reason for this is that the condition is more lethal in boys, who die intrauterinely”, said Marion.

As identified by www.trisomy18.org, there are typical characteristic of Trisomy 18 which include:

    Heart defects:
        VSD (Ventricular Septal Defect): a hole between the lower chambers
        ASD (Atrial Septal Defect): a hole between the upper chambers
        Coarctation of the aorta: a narrowing of the exit vessel from the heart
    Kidney problems
    Part of the intestinal tract is outside the stomach (omphalocele)
    The esophagus doesn’t connect to the stomach (esophageal artesia)
    Excess amniotic fluid (polyhydramnios)
    Clenched hands
    Pocket of fluid on the brain (choroid plexus cysts)
    Rocker bottom feet
    Delayed growth
    Small jaw (mycrognathia)
    Small head (microcephaly)
    Low-set ears
    Strawberry-shaped head
    Severe developmental delays
    Umbilical or inguinal hernia

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