Down’s Syndrome

Genetic disorder due to trisomy 21, associated with:

Epidemiology and Risk Factors

Down’s syndrome is:

  • The most common chromosomal disorder
    ~1/700 live births.

Risk factors:

  • Maternal age
    • 1/1400 at 25
    • 1/46 at 45
  • Previously affected child

Pathophysiology

Aetiology

Predominantly due to trisomy 21. Remainder are:

  • Chromosomal translocation
    ~4% of cases.
  • Mosaic trisomy 21
    ~1% of cases.

Clinical Manifestations

History

Examination

Characteristic facies:

  • Brachycephaly
    Disproportionately wide head.

  • Third fontanelle

  • Flat nasal bridge

  • Epicanthic folds
    Skin fold covering medial canthus.

  • Upwardly slanting palepbral fissues

  • Small mouth

  • Small ears

  • Single palmar crease
    Occurs in 50%.

  • Often low birth weight in infancy, with obesity in adulthood

Diagnostic Approach and DDx

Investigations

Management

Anaesthetic Considerations

  • A
    • Airway difficulty
      Despite the below changes, muscular hypotonia makes laryngoscopy generally straightfoward.
      • Macroglossia
      • Micrognathia
      • Midface hypoplasia
      • Short neck
      • Tonsillar hypertrophy
    • Atlanto-axial instability
      • Cord compression symptoms may develop post-operatively in previously asymptomatic individuals
      • Asymptomatic in 10-20%
      • Symptomatic in 1.5%
    • Subglottic stenosis
      In ~5%. Use smaller ETT than expected for age.
    • Recurrent RTIs
      Due to immune deficiency.
  • B
    • High incidence of post-operatively respiratory complications
    • Impaired central respiratory drive
    • Chronic lower respiratory tract infections are common
      • Impaired immunity
      • GORD
      • Hypotonia
    • OSA
      • Due to craniofacial abnormalities
      • Present in 50-75%
  • C
    • Bradycardia common and significant with anaesthetic agents
      Have atropine available.
    • Strong association with congenital heart disease
      In ~60%.
      • Common abnormalities
        • ASD
        • VSD
        • PDA
        • TOF
      • Pulmonary HTN develops earlier and more severely than non-DS patients
  • D
    • Intellectual impairment
      Mean IQ ~50 in adulthood.
    • Agitation
      Post-operatively.
    • Epilepsy
      In ~10%.
  • E
    • Generalised hypotonia
  • G
    • GORD
  • H
    • Prone to polycythaemia
    • Higher incidence of leukaemias
  • I
    • Immune dysfunction
      General abnormalities in T cell, B cell, gamma globulins, and neutrophil function.

Marginal and Ineffective Therapies

Complications

Prognosis

Mortality:

  • Life expectancy generally good in developed world
  • ~20% die in first year of life
  • 45% survive until 60

Key Studies

References

  1. Allt, Jules E, and Charlotte J Howell. ‘Down’s Syndrome’. BJA CEPD Reviews 3, no. 3 (June 2003): 83–86. https://doi.org/10.1093/bjacepd/mkg083.