Edwards syndrome


Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of all, or part of a third copy of chromosome 18.

Affect 1 in 6000 births.

The presence of an extra copy of genetic material on the 18th chromosome, either in whole (trisomy 18) or in part (such as due to translocations).

The additional chromosome usually occurs before conception.

More prevalent in female offspring.

Babies are often born small have heart defects, small heads, overlapping fingers, clenched fists and are intellectually disabled.

Most cases occur during the formation of the reproductive cells or during early development.

The rate of disease increases with the mother’s age.

Rarely inherited as occasionally not all cells have the extra chromosome, known as mosaic trisomy.

With mosaic trisomy symptoms may be less severe.

Ultrasound in uterus can suggest the condition, which can be confirmed by amniocentesis.

Treatment is supportive.

After having one child with the condition, the risk of having a second is typically around one percent.

It is the second-most frequent condition due to a third chromosome, after Down syndrome.

Edwards syndrome occurs in around one in 5,000 live births.

Most babies born with the condition are female, and many affected die before birth.

Survival beyond a year of life is around 7.5%.

Clenched hand and overlapping fingers are characteristically seen in trisomy 18.

Patients may have kidney malformations, structural heart defects, omphalocele, esophageal atresia, intellectual disability, developmental delays, growth deficiency, feeding difficulties, breathing difficulties, and arthrogryposis.

Some physical malformations associated include microcephaly, prominent back portion of the head, low-set, malformed ears, micrognathia, cleft lip/cleft palate, upturned nose, narrow eyelid folds, hypertelorism, ptosis), a short breast bone, clenched hands, choroid plexus cysts, underdeveloped thumbs and/or nails, absent radius, webbing of toes, clubfoot, and in males, undescended testicles.

In utero, the most common characteristic is cardiac anomalies, followed by central nervous system anomalies such as head shape abnormalities.

The most common intracranial anomaly is the presence of choroid plexus cysts, which are pockets of fluid on the brain.

The presence of choroid plexus may be a marker for trisomy 18.

Errors can arise at either of the two meiotic divisions and cause the failure of a chromosome to segregate into the daughter cells, resulting in an extra chromosome, making the haploid number 24 rather than 23.

Fertilization of eggs that contain an extra chromosome results in trisomy, or three copies of a chromosome rather than two.

Trisomy 18 (47,XX,+18) is caused by a meiotic nondisjunction event, with an extra copy of chromosome 18

Such an embryo has 47 chromosomes, with three copies of chromosome 18.

In a small number of cases, only some of the body’s cells have an extra copy of chromosome 18, resulting in a mixed population of cells with a differing number of chromosomes, ref2242ed to as mosaic Edwards syndrome.

With a translocation of chromosome 18 to another chromosome a person often has a less severe process.

Major causes of death include apnea and heart abnormalities.

About half of the infants with this condition do not survive beyond the first week of life, and the median lifespan is five to 15 days.

About 8% of infants survive longer than 1 year and 1% live to age 10, typically in less severe cases of the mosaic Edwards syndrome.

While the syndrome occurs in about one in 5,000 live births, more conceptions are affected by the syndrome because the majority will not survive the prenatal period.

The risk of conceiving a child with it increases with a woman’s age, and average maternal age for conceiving a child with this disorder is 32½.

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