Down's Syndrome

  • Trisomy 21 (90%) of cases

Typical Patient

  • congenital

  • Risk related to increasing maternal age

    • 1 in 650 overall

    • 1 in 1000 at age 20,

    • >40 - 1 in 100

    • >45 - 1 in 30

    • 70-80% born to women <35 due to number of babies born

Symptoms / Signs

Features of Down's syndrome

  • Eyes

    • narrow palpebral fissures

    • almond shaped eyes

    • epicanthic folds

    • ophthalmic defect

    • Brushfield spots

      • small streaks on the iris

  • Ears

    • simple

    • small lobes

  • Hands and Feet

    • small hands

    • single palmar crease on hands and feet

    • incurving fifth fingers

    • widely spaced first and second toes

  • Increased risk of duodenal atresia and Hirschsprung disease

  • Congenital Heart disease (75%)

    • severe in 20-40%

    • commonly simple ventricular septal defect or atrioventricular canal defect

    • may be tetralogy of Fallot

  • Increased risk of later disease

    • profound myopia

    • deafness

    • leukaemia - acute childhood

    • premature senility

      • Alzheimer-like degeneration after 40 (60-70%)

  • Moderate to severe learning difficulties - IQ 20-80

  • Gastrointestinal defects

Other signs at birth

  • poor muscle tone

  • poor feeding

  • mild jaundice

Variants

  • Mosaicism

    • much better prognosis

  • 10% have balanced translocation

    • 20-40% of parents have balanced translocation in their cell line with 1 in 2 risk of baby with Down's syndrome

Pathology

  • Trisomy 21 (90%)

  • Balanced translocation involving chromosome 21 (10%)

Investigations

Screening

  • maternal

    • serum beta-HCG

    • alpha-fetoprotein

    • gives risk of Down's - greater than 1/250 is high risk and should have amniocentesis

  • nuchal translucency on ultrasound scan

    • thickened, oedematous flap of skin at base of neck

  • amniocentesis - 1% risk of loss

    • karyotyping

Treatments

  • counselling for parents

    • suggest joining Down's Parents' association or similar

  • support for visual / hearing problems

  • suitable schooling

Prognosis

Mortality

  • high in first year

  • some survive into adulthood

Complications

  • see features

 

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