Genetics: Edwards Syndrome Flashcards
What type of disorder is Edwards syndrome?
A chromosomal disorder
What chromosome is there an extra copy of?
Chromosome 18
What is Edwards syndrome also known as?
Trisomy 18
Is it the second or third most common trisomy?
Second after Down syndrome
What process accounts for most of the cases of trisomy 18?
Nondisjunction - the chromosomes do not split apart
One cell ends up with both chromosomes and the other none
What process accounts for a small percentage of trisomy 18 cases?
Robertsonian translocation
Part of one chromosome switches places with part of another chromosome
One of these needs to be chromosome 18, but the other can be any chromosome
Hybrid long arms and short arms (shorts arms typically lost)
Does it have an effect on almost every organ system in the body?
Yes
Overexpression of the genes on chromosome 18, leading to abnormal development of all types of cells
What gastrointestinal anomalies occur?
Omphalocele
Oesophageal atresia - causing polyhydramnios
What kidney malformations can occur?
Horseshoe kidney
Other than GI and kidney malformations, what other complications are associated?
Congenital heart defects - PDA, septal defects
Intellectual disability
Failure to thrive
Frequent infections
Breathing problems - due to pulmonary hypoplasia
What tumour do they have an increased risk of developing?
Nephroblastoma (Wilms tumour) and hepatoblastoma
What risk factors are there?
Advancing maternal age
FH - after having one child with Edwards syndrome, the risk increases
Is it more common in male or females?
Females 3x
Do most babies with Edwards syndrome die before birth?
Yes
What clinical features are associated?
Prominent occiput Microcephaly Small mouth and chin Low set ears Short sternum Flexed, overlapping fingers Rocker bottom feet Cleft lip and palate
