Edward’s Syndrome

Overview – Edward’s Syndrome

Edward’s syndrome, also known as Trisomy 18, is a serious chromosomal disorder caused by the presence of an extra copy of chromosome 18. It is associated with severe developmental and physical abnormalities, and while most affected pregnancies do not result in live births, some children may survive beyond infancy, particularly in mosaic or partial forms. Understanding its variants, clinical features, and diagnostic methods is essential for antenatal screening and paediatric management.

Definition

Edward’s syndrome (Trisomy 18) is a genetic disorder characterised by the presence of three copies of chromosome 18 (instead of two) in some or all cells of the body. It results in multiple congenital anomalies and significant developmental delay.

Aetiology

• Genetic Cause:
  • Trisomy 18: Caused by nondisjunction during meiosis in either oogenesis or spermatogenesis
  • 47, XY, +18 indicates a male with an extra chromosome 18

Types

Full Edwards Syndrome

• Trisomy 18 in all cells
• Most severe presentation
• High rates of stillbirth

Mosaic Edwards Syndrome

• Trisomy 18 in some cells
• Milder presentation
• Greater chance of survival beyond infancy; some reach adulthood

Partial Edwards Syndrome

• Only a segment of an extra chromosome 18 present
• Highly variable presentation depending on which genes are affected

Clinical Features

• Intrauterine growth restriction (low birth weight)
• Congenital heart defects
• Pulmonary and renal malformations
• Flexion deformities of fingers (clenched fists with overlapping fingers)
• Prominent occiput (back of the skull)
• Neural tube defects (e.g. spina bifida)

Investigations

Antenatal Screening

• Combined First Trimester Test (10–14 weeks):
  • Nuchal translucency on ultrasound
  • Maternal serum markers (PAPP-A and hCG)
  • Screens for Edward’s syndrome, Down’s syndrome, and Patau’s syndrome

Diagnostic Testing (if high-risk screening result):

• Chorionic Villus Sampling (CVS):
  • Sampling of placental tissue (early as 11 weeks)
• Amniocentesis:
  • Sampling of amniotic fluid (typically from 15 weeks onwards)
• Karyotyping or FISH analysis confirms trisomy

Management

• No curative treatment
• Supportive care based on specific anomalies:
  • Management of cardiac or respiratory issues
  • Feeding support and nutritional care
  • Physiotherapy and occupational therapy
  • Palliative care may be considered for severe cases

Prognosis

• Full Edwards syndrome:
  • Median survival is days to weeks
  • 90% die within the first year of life
• Mosaic and partial forms:
  • Longer survival possible
  • Developmental disability common

Summary – Edward’s Syndrome

Edward’s syndrome (Trisomy 18) is a chromosomal condition resulting from an extra copy of chromosome 18. It causes significant congenital abnormalities and often leads to stillbirth or early neonatal death in its full form. Milder variants, such as mosaic or partial forms, may allow survival into childhood or even adulthood. Diagnosis relies on prenatal screening and confirmatory genetic testing. For more, visit our Genetics & Cancer Overview page.