Edward Syndrome, also known as Trisomy 18, is a severe chromosomal disorder caused by the presence of an extra chromosome 18. It leads to a range of severe developmental and physical abnormalities.
Overview of Edward Syndrome (Trisomy 18)
Genetic Cause:
Chromosomal Basis: Edward Syndrome results from the presence of an extra chromosome 18. This can be due to nondisjunction during the formation of reproductive cells, which results in three copies of chromosome 18 in the fertilized egg.
Genetic Mechanisms: It can occur in a full trisomy (where every cell has an extra chromosome 18), mosaic trisomy (where only some cells have an extra chromosome 18), or partial trisomy (where part of the chromosome is extra).
Incidence:
Edward Syndrome is the second most common trisomy after Down syndrome (Trisomy 21). It occurs in approximately 1 in 5,000 live births.
Clinical Features:
Growth Retardation: Infants often have low birth weight and exhibit slow growth.
Craniofacial Abnormalities: Includes micrognathia (small jaw), low-set ears, prominent occiput (back of the head), and a small mouth.
Hand Abnormalities: Clenched hands with overlapping fingers are characteristic.
Foot Abnormalities: Rocker-bottom feet (rounded bottom) are common.
Cardiac Defects: Congenital heart defects such as ventricular septal defects (VSDs) and atrial septal defects (ASDs) are prevalent.
Organ Malformations: These include renal abnormalities, gastrointestinal malformations, and diaphragmatic hernia.
Neurological Issues: Severe intellectual disability and brain anomalies.
Feeding and Breathing Difficulties: Often due to abnormalities in the muscles and organs involved in these processes.
Diagnosis:
Prenatal Screening: Ultrasound, maternal serum screening, and non-invasive prenatal testing (NIPT) can suggest the possibility of trisomy 18.
Diagnostic Testing: Amniocentesis or chorionic villus sampling (CVS) followed by karyotyping can confirm the diagnosis.
Postnatal Diagnosis: Physical examination and chromosomal analysis of the infant.
Prognosis:
Edward Syndrome is associated with high mortality; many affected infants do not survive beyond the first few weeks or months of life. Some may survive longer with intensive medical care, though they typically have severe disabilities and health challenges.
Management:
Supportive Care: Focuses on managing symptoms, including feeding support, surgical interventions for malformations, respiratory support, and physical therapy.
Palliative Care: Often provided to manage symptoms and improve quality of life, especially given the poor long-term prognosis.
Genetic Counseling: Helps families understand the condition, recurrence risks, and implications for future pregnancies.
Additional Information:
Epidemiology: Edward Syndrome affects both males and females, but slightly more females are affected.
Associated Risks: The risk of having a child with Edward Syndrome increases with maternal age, though it can occur in any pregnancy.
Prevention: There are no known prevention measures due to its spontaneous occurrence. However, prenatal screening and genetic counseling are vital for at-risk populations.