Down Syndrome

Question 1

Definition of DS

Answer 1

Genetic syndrome relating to an abnormality associated with chromosome 21.
- Comprises of several specific physical and psychological features and increased risk of medical complications

Question 2

Causes of DS

Answer 2

95% of cases has extra copy of chromosome 21 occurring in developing foetus resulting in child being born with 47 chromosomes in each cell instead of 46 - changes normal development of the brain

Question 3

Risk Factors of DS

Answer 3

• Increased risk with increasing age of mother

- Previous birth of baby with DS

Question 4

Epidemiology - Incidence (DS)

Answer 4

• Most common genetic disorder causing intellectual disability
• Occurs in approx. 1 in 1000 live births (higher rates 25/2000 in women at age 45)

Question 5

Pathophysiology of DS

Answer 5

Normal number of chromosomes = 46 (23 pairs)

• Abnormal cell devision during formation of an egg or sperm results in additional copy of chromosome 21 and total of 24 chromosomes from either mother or father
• Therefore after fertilisation with a sperm or egg with 23 chromosomes, the resulting embryo contains 47 chromosomes = Malformations and developmental abnormalities

Question 6

Clinical Features:

Physical Features

Answer 6

• Facial: Upward slant to eyes, small ears, flatter facial profile than usual, white spots in iris of eyes
• Short neck
• Low muscle tone, loose ligaments
• Small hands and feet
• Short stature

Question 7

Clinical Features:

Delayed Motors development and varying levels of intellectual disability

Answer 7

• Delay in motor milestones e.g. sitting, standing, walking, fine motor skills
• Delay in acquiring spoken language BUT socially responsive
• Mild to Moderate cognitive impairment = more obvious in older childhood because intellectual ability develops more slowly than normal
• Autism and ADD common in DS children

Question 8

Clinical Features:

Associated health conditions

Answer 8

• Congenital heart defects, hearing loss, eye problems, gastrointestinal problems, thyroid dysfunction, low resting metabolic rate, increased risk of weight gain, musculoskeletal problems (hypotonia)

Question 9

Diagnosis of DS

Answer 9

Before birth:

• Screening through blood tests and ultrasound
• Diagnostic testing with aminocentesis for older women

After birth:
Clinical observation combined with blood test to confirm DS

Question 10

Interdisciplinary Management of DS

Answer 10

• Routine monitoring of possible medical conditions starting in infancy e.g. eye, hearing, heart disease, diabetes, hypothyroidism
• Monitoring and treatment of mental health disorders such as depression in later life (30%)
• Surgery for heart defects
  Info and support for parents along with genetic counselling

Question 11

Prognosis of DS

Answer 11

Average life expectancy = mid 50’s (affected by effective management of medical conditions associated with DS)

Question 12

Differential Diagnosis of DS

Answer 12

Other chromosomal abnormalities such as Prader-Willi syndrome