Downs syndrome

Question 1

Incidence

Answer 1

• 1/1000 live births
• 1/2500 in women less than 30
• 1/80 over 40
• 1/32 over 45

Question 2

Genetics

Answer 2

• Full trisomy 21 (non-disjunction) is seen in 92-95%
• Robertsonian translocation 2-4%
• Mosaic in 1-2.5

Question 3

Clinical features

Answer 3

• general hypotonia
• oblique palpebral fissures
• small flattened skull
• high cheekbones
• protruding tongue
• short stature
• overweight
• brachycephaly, high arched palate
• brushfield spots in iris
• epicanthic fold
• low set ears
• short broad hands with a single palmar crease
• syndactyly, clinidactyly, altered dermatoglyphics

Question 4

Congenital defects

Answer 4

• congenital heart defects in 50%
• VSD, mitral valve disease, PDA
• GI abnormalities-oesphageal atresia, hirschsprung disease, umbilical and inguinal hernia
• strabismus and myopia
• otitis media
• sensorineural deafness
• hypothyroidism and diabetes

Question 5

Learning disability

Answer 5

• average IQ is 50
• mental development progresses normally from birth to 6 months of age
• gradual decrease in IQ over time

Question 6

Neuropathological changes

Answer 6

• similar to AD

- senile plaques and neurofibrillary tangles are seen

Question 7

Dementia

Answer 7

• 0.4% under 30 years
• 2-33% in 30-39
• 8-55% for 40-49
• 20-55% for 50-59
• 29-75% for 60-69
• all over 40 show neuropathology but may not have clinical dementia
• use Dementia Questionnaire for persons with mental retardation (DMR)

Question 8

Epilepsy

Answer 8

• seen in 10% adults with Down syndrome
• 40% in those over 40
• 80% in those with Alzheimers and Downs

Question 9

Cause of death

Answer 9

• highest absolute risk is below the age of 1 where congenital heart disease predominates as cause
• pneumonia and other infections is the commonest cause of death up to the age of 30