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Down’s syndrome

Specialties > Child health

Background knowledge 🧠

Definition

  • Down’s syndrome (Trisomy 21) is a genetic disorder caused by the presence of an extra copy of chromosome 21.
  • It is associated with intellectual disability, characteristic facial features, and various congenital anomalies.

Epidemiology

  • Incidence is approximately 1 in 700 live births in the UK.
  • Risk increases with maternal age, especially over 35 years.
  • Most common chromosomal abnormality causing intellectual disability.

Aetiology and Pathophysiology

  • Trisomy 21: Most common form, caused by nondisjunction during meiosis.
  • Mosaicism: Presence of a mixture of normal and trisomy 21 cells, less severe phenotype.
  • Robertsonian Translocation: Part of chromosome 21 attaches to another chromosome, often chromosome 14.
  • The extra genetic material leads to the characteristic features and developmental issues.

Types

  • Trisomy 21 (94% of cases).
  • Mosaic Down’s syndrome (1-2% of cases).
  • Robertsonian Translocation (3-4% of cases).

Clinical Features 🌡️

Symptoms

  • Developmental delay.
  • Intellectual disability.
  • Hypotonia (low muscle tone).
  • Learning difficulties.
  • Increased risk of infections.
  • Hearing loss.

Signs

  • Flat facial profile with upward slanting eyes.
  • Single palmar crease.
  • Short neck with excess skin at the nape.
  • Brushfield spots (white spots on the iris).
  • Short stature.
  • Congenital heart defects (e.g., AVSD, VSD).
  • Sandal gap (increased space between the first and second toes).

Investigations 🧪

Tests

  • Prenatal screening: Combined test (nuchal translucency, PAPP-A, beta-hCG).
  • Non-invasive prenatal testing (NIPT): Detects fetal DNA in maternal blood.
  • Amniocentesis or Chorionic Villus Sampling (CVS): Confirmatory karyotyping.
  • Postnatal: Karyotype analysis to confirm diagnosis.
  • Echocardiogram: To assess for congenital heart defects.
  • Hearing and vision tests: Routine monitoring due to high risk of impairment.

Management 🥼

Management

  • Multidisciplinary approach involving paediatricians, cardiologists, ENT specialists, and developmental therapists.
  • Early intervention programs to support development.
  • Regular monitoring for common complications (e.g., hypothyroidism, coeliac disease).
  • Management of cardiac anomalies, often requiring surgery.
  • Parental support and genetic counselling.

Complications

  • Congenital heart defects: Most common, especially AVSD.
  • Hypothyroidism: Regular thyroid function testing recommended.
  • Respiratory infections: Increased susceptibility, often due to airway anomalies.
  • Gastrointestinal anomalies: e.g., Duodenal atresia.
  • Increased risk of leukemia and other malignancies.
  • Atlantoaxial instability: Risk of spinal cord compression.
  • Hearing loss: Conductive or sensorineural.

Prognosis

  • Life expectancy has improved significantly, with many living into their 60s.
  • Quality of life depends on the severity of complications and access to supportive care.
  • Increased risk of Alzheimer’s disease in later life.

Key Points

  • Early diagnosis and intervention are crucial for improving outcomes.
  • Multidisciplinary management is essential for addressing the complex needs of patients.
  • Ongoing research is focused on improving quality of life and understanding genetic mechanisms.

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Child health