Intellectual Disability Flashcards
how is intellectual disability defined?
neurodevelopmental disorder that begins in childhood and is characterised by limitations in both intelligence and adaptive skills.
what are the three domains of adaptive skills?
conceptual
social
practical
what is meant by conceptual adaptive skills?
language, reading and writing (literacy), money, time, reasoning, memory and judgment
what is meant by social adaptive skills?
interpersonal social communication, empathy, relating to peers, social responsibility, the ability to follow rules, self-esteem
what is meant by practical adaptive skills?
activities of personal care or daily living like eating dressing, mobility.
following a schedule/routine, managing money, preparing meals, ability to travel, health care and safety
what are the causes of ID?
> 50% genetic = e.g downs syndrome and mitochondrial disorders
environmental = perinatal and postnatal causes
what are some examples of environmental causes of ID?
perinatal = anti epileptic drugs
pre/post natal = infection
post natal = trauma asphyxia (lack of O2)
why are ID complex?
multimorbidites
polypharmacy
multi-professionals
what is the prevalence of ID in the UK?
1.5 million - 300,000 have severe ID
many undiagnosed/misdiagnosed
outline the criteria for ID
intellectual impairment IQ</=70
social/adaptive dysfunction
onset during developmental period
what is LeDeR?
learning disabilities mortality review - created because people with learning disabilities were dying prematurely
its a primary care research database
what are some statistics of the LeDeR
people with ID had life expectancy 19.7yrs lower
a third of deaths of people with LD were from treatable medical causes compared to 8% in general population
people with LD died from avoidable medical causes 2x as frequently as general population
how did COVID-19 affect people with LD differently?
4x increase risk for COVID hospitalisation and 10x increased risk for COVID death in downs syndrome people
COVID death rate was 2.3 times higher for people with LD
outline autism spectrum disorder
developmental disorder
issues with social communication, interaction and restricted, repetitive patterns of behaviour, interests and activities
different ways of learning, moving or paying attention
outline what is meant by difficulty with social communication in ASD?
difficulty interpreting verbal/nonverbal language like gestures or tone of voice
taking things literally
needing extra time to process information
repeating what others say to them (echolalia)
outline what is meant by difficulty with social interaction in ASD?
difficulty ‘reading’ others and expressing own emotions, so autistic people may appear insensitive, seek out time alone, not seek comfort from people, behave ‘strangely’ or in socially inappropriate way
hard to form friendships
outline repetitive behaviours as a symptom of ASD
world is unpredictable to autistic people, so they prefer routine e.g eat exactly the same food for breakfast/wear same clothes
repeat movement like hand flapping, rocking to calm themselves when stressed or because they find it enjoyable
change to routine is distressing - makes them anxious e.g changing schools
outline sensory sensitivity as a symptom of ASD?
over/under sensitivity to sounds touch tastes smells light temperature or pain
e.g background music in a restaurant they find unbearably loud and distracting
many people prefer not to hug due to discomfort too
outline the behavioural symptoms of someone with ASD?
highly focused hobbies
anxiety
meltdowns/shutdowns
- completely overwhelmed - temporarily loses behavioural control or more passive like switching off
what is meant by STOMP-STAMP?
NHS england
stopping overmedication of people with learning disabilities, autism or both
a lot of drugs have psychiatric side effects
clinical approach to prescribing drugs
always personalise treatment
use lowest dose possible and escalate slowly
what was the scandal between epilepsy and ID?
in 2002, Marson AG et al. Valproate was most effective anti-epileptic, widely prescribed
pregnant women who took it = children had developmental disorders and cleft lips, children had significantly lower IQ score
patients liked drug and had high probability to remain on it
how does the DSM diagnose intellectual disability?
onset during developmental period, deficit in conceptual, social and practical domains
deficits in adaptive functioning - how well people cope with common life demands
mild mental retardation IQ = 50-70
moderate = 35-55
severe = 20-40
profound retardation IQ below 25
is a child bangs their head at age 8 and has cognitive vulnerabilities what are they likely to be diagnosed with compared to an adult?
child - ID because of onset age and due to brain developing until 18,
adult would be diagnosed with acquired head injury
what is the connection between ID and epilepsy?
moderate/severe/profound ID means higher risk of epilepsy
genetics of epilepsy overlap with those of ID
how have the rates of ID and autism changed over time comparatively?
as rates of autism grew, ID rates were declining - no biological reason - both at steady 2% of population
another explanation is that doctors were using ‘autism’ to describe children with ID as autism diagnosis gets a lot of service e.g 1 to 1 school and government support
outline aetiology of ID across developmental stages
prenatal - fetal alcohol disorder - limits of this not well defined,
idoine deficiency - childhood to adulthood - cause of ID
genetics - myelination, polygenic inheritance
what are the 4 technologies for elucidating genes
karyotyping
FISH
microarray
sequencing
what is karyotyping
staining and visualising chromosomes, easy to do, not good resolution but can see large things - detects aneuoploidy., translocations and large inversions
what is FISH
hybridize probe known to be attracted to particular area of genome, finds identical partner, can see through fluorescence, not good resolution but can see microdeletions and duplications
whole genome sequenicng is what is done nowadays
what would the karyotype of someone with downs syndrome look like?
extra chromosome e.g 3 chromosome 21s.
how would a karyotype of Fragile X syndrome look?
trinucleotide repeat expansion CGG - tip of X chromosome is slightly attenuated (longer)
syndrome associated with sutism, social phobia (agoraphobia).
most common inherited cause of ID
outline downs syndrome
commonest GENETIC form of ID, multi-system pathology
some people will have normal IQ
need to check for hyper/hypothyroidism
greater risk of early onset dementia - but how do they diagnose someone non-verbal?
are there a lot of single gene disorders linked with ID?
yes around 1000, they are everywhere but not on the Y chromosome, more striking abnormalities are on X chromosomes and there are a lot more of these
what are some X linked IDs and what is the gene mutation that causes them
RETT syndrome, severe autism intellectual disabilities are caused by MECP2 gene disorder
what is genetic pleiotropy?
when one gene influences 2 or more seemingly unrelated phenotypic traits
how does pleiotropy relate to ID?
e.g genes that cause autism can also cause schizophrenia
and epilepsy
how many autism genes have been identified?
500 possible autism genes equally spread out over chromosomes
outline how autism arises from genetic mutations?
most autism is caused by copy number variation (micro deletions and micro duplications),
the most common copy number variant of autism is 16P11.2
also causes obesity
what disorder does ID polygenicity overlap with significantly?
ADHD
is there a lot of polygenic risk within ID?
not a lot of evidence for this, we all have common genetic variation with polymorphisms across genes (2+ possibilities of a trait on a gene),
if someone has a particular variant at many sites, it will push them over the threshold to have a related phenotype
explain polygenic risk in terms of parents
e.g if parents are fine but child has 1 risk allele they could still have ASD if it is a de novo deleterious mutation but this is rare
but, also when polygenic risk is high e.g one parent has 50 polymorphisms and another has 150 when they reproduce the offspring is over the threshold and has ASD
what do a lot of ID genes do?
converge
