Edwards' syndrome (trisomy 18)
Edwards' syndrome, also known as trisomy 18, is a genetic condition that arises when there is an extra copy of chromosome 18 in a person's cells. This additional chromosome disrupts normal development, leading to a range of serious health issues.
Symptoms of Edwards' syndrome can vary but often include severe developmental delays, low birth weight, and distinctive physical features such as a small head, a prominent back of the head, and clenched fists. Other common signs may include heart defects, kidney problems, and feeding difficulties.
There are typically two types of trisomy 18: full trisomy 18, where all cells have the extra chromosome, and mosaic trisomy 18, where only some cells have the additional chromosome. The mosaic form tends to be less severe than the full form.
Diagnosis of Edwards' syndrome usually involves prenatal screening tests, such as blood tests and ultrasound scans, which may indicate a higher risk. If there are concerns, further diagnostic procedures like amniocentesis or chorionic villus sampling (CVS) can confirm the presence of the extra chromosome.
The exact cause of trisomy 18 is not fully understood. However, it is generally believed to occur due to random errors during cell division, leading to the formation of an egg or sperm with an abnormal number of chromosomes. Advanced maternal age is also a known risk factor for having a baby with this condition.