Down syndrome – Basics

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What is Down syndrome?

  • Down Syndrome (DS) is a genetic disorder due to chromosomal number alteration. The other name of this disease is Trisomy 21. Here, an additional copy of chromosome number 21 is present.

Incidence

  • The worldwide incidence of Down Syndrome is 1.5 per 1000 live birth.
  • Increased maternal and paternal age plays a pivotal role in Down syndrome.
  • The incidence of Down syndrome increase with the progression of maternal age.
  • The probability increases from less than 0.1% in 20-year-old mothers to 3% in 45-year-old mothers.

Features

  • Face:
    • Upslanting palpebral fissures 
    • Epicanthic folds
    • Brushfield spots in the iris
    • Tongue protrusion
    • Low set small ears
    • Flat or round face
  • Flat occiput
  • Single palmar crease
  • Marked ‘sandal gap’ between the big toe and first toe
  • Decreased muscle tone
  • Short stature

Complications

  • Cardiac
    • Ventricular septal defect (the most common cardiac problem)
    • Cushion defect of the endocardium
    • Tetralogy of Fallot (TOF)
    • Ostium secundum atrial septal defect (ASD)
    • Patent ductus arteriosus (PDA)
  • Neurological
  • Others
    • Acute lymphoblastic leukemia
    • Recurrent respiratory infection
    • Hypothyroidism
    • Male infertility
    • Female subfertility
    • Atlantoaxial instability

Diagnosis

  • Screening
    • Blood test – pregnancy-associated plasma protein-A (PAPP-A)
    • Nuchal translucency test
  • Diagnostic
    • Chorionic villus sampling 
    • Amniocentesis

Treatment

  • No definitive treatment has been yet established.
  • Symptomatic and interventional treatments are given for associated critical conditions. Usually, the multi-disciplinary medical team is needed. 
  • Support groups.

Life expectancy

  • Around 20% of patients die within the 1st year. 
  • 45% may survive up to 60 years.
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