Fragile X syndrome

Question 1

prevalence?

Answer 1

1 in 4000 males

1 in 6000 females

Question 2

features?

male/ female difference - why?

Answer 2

impaired cognitive ability
less severe symptoms in females
–> second X chromosome in females appears to be somewhat protective (XX)

Question 3

caused by?

Answer 3

expansion of CGG repeat at the beginning of FMR-1 gene on the X chromosome
normal: 5 - 50 repeats
premutation: 50-200 repeats
full mutation = 200-2000 repeats
(no. of repeats on the allele based on the size of the CGG expanded region)

Question 4

identifiable how? (eg. diagnosis)

-typical age of diagnosis?

Answer 4

DNA blood test
FXS is the most common form of inherited intellectual disability
typically diagnosed at 3 - 4 yead

Question 5

Grey matter contains?

White matter contains?

Answer 5

Grey matter = cell bodies, dendrites and axon terminals of neurons = where all synapses are (Structure)
White matter = axons connecting different parts of grey matter to each other (connection between areas)

Question 6

Differences in the brain? (age 1-3 years)
grey matter
white matter

Answer 6

voxel-wise grey and white matter volumes comparison in 1-3 yr old boys with FXS:
- enlarged GMV in caudate, thalamus and fusiform gyrus
- reduced GMV in cerebellar vermis
- greater WMV of striatal- prefrontal regions
suggests: early, possibly prental, genetically mediated alterations in neurodevelopment
(method = compare scans to scans of children who are neurotypical)

Question 7

Physical features

- common features?

Answer 7

long/narrow face
prominent jaw
prominent ears
flat feet
common features:
short attention span, distractibility, impulsiveness, restlessness, overactivity (similar to ADHD), sensory problems, social difficulties, communication difficulties (autistic features)

Question 8

co-morbidity?

Answer 8

dual-diagnosis of autism is common (Bailey et al)

• 50-90% have ‘autistic symptoms’
• 25-80% have ASD diagnosis
• poor eye contact, hand flapping, perseveration
• prevalence of ADHD symptoms in children with FXS is between 54% and 59% (Sullivan et al)
• epilepsy is quite common

Question 9

strengths in those with FXS?

Answer 9

imitation
visual learning
personable (eg. sensitive and sense of humour)

Question 10

Cogntiive and behavioural profile?

male and female

Answer 10

males:
-mean IQ = 40
-communication impairment
-language deficit
-social impairment (especially anxiety)
-hyperactivity, inattention, impulsivity, hyperarousal
(males suffer more severe IQ problems)
females:
- mean IQ= 70
- social difficulties
-emotional/ anxiety/ depression
(females suffer more social/emotional problems)

Question 11

First signs?

Answer 11

sensoy-motor atypicalities at 9-12 months
-decreased object play, increased leg stereotypies, atypical posturing, prolonged visual attention to objects
- missing milestones/ atypical dev
= may alert parents to seek medical advice and access diagnostic services

Question 12

Adaptive behaiour

Answer 12

measured via Vineland adaptive behaviour scales
- assessed ‘real life skills’ and ‘independence’
- semi-structured parent interview
-communication, daily living, socialisation, motor skills
adaptive behaviour outcomes
- variable trajectory
-positive environmental influences may act as protective factors (Glaser et al, 2003)
eg. parental expectations, parenting skill , emotional climate, organisation of the home

IQ was the strongest predictor of outcomes
its important to consider early predictors of risk and experience