98b - Intellecutal Disability

Question 1

What is the most common cause of mild intellectual disability?

Answer 1

Familial Intellectual Disabilty

Usually IQ > 50

(Often, people with mild intellectual disability have family members with mild ID; Intelligence is highly heritable)

Question 2

The majority of people with Intellectual Disability have an IQ of [range]

Answer 2

The majority of people with Intellectual Disability have an IQ of 50-70

This is considered “mild” intellectual disability

Can receive an education, may live independently

Question 3

What is the most common inherited (genetic) cause of intellectual disability?

Answer 3

Fragile X syndrome

• caused by trinucleotide repeat expansion of FMR1 gene on X chromosome ® decreased production of FMRP, which is involved in synaptic plasticity
  
  • pre-mutation refers to 55-200 repeats, while full mutation refers to > 200 repeats, which results in methylation/silencing of the gene
  • no father to son transmission
  • characterized by large ears, long face, prominent jaw, connective tissue abnormalities, mitral valve prolapse

Question 4

What is the mean and standard deviation for IQ?

Answer 4

Mean = 100

Standard deviation = 15

• IQ test ~ 70 indicates a limitation in intellect (below 2 SD of the mean)

Question 5

At which stage of development does intellectual disability most often begin?

Answer 5

Prenatal development

Includes the following etiologies:

• Chromosomal (Down Syndrome)
• Single gene (Fragile X)
• Malformation syndromes
  
  • Neural tube, hydrocephalus, microcephaly, anencephaly

Question 6

List 3 causes of intellectual disability with postnatal origin

Answer 6

• Hypoxic birth injury
• Brain injury
• Metabolic disorders
  
  • Technically the mutation is there prenatally, but no pathologic changes have occured until the postnatal period

Question 7

Give an example of a cause of intellectual disability with perinatal origin

Answer 7

Infectious disease

Question 8

IQ < __ defines intellectual disability

Answer 8

IQ 70 defines intellectual disability

Standard Deviation = 15

<70 is more than 2 standard deviations below the mean

Question 9

What is the most common chromosomal cause of intellectual disability?

Answer 9

Down Syndrome

Question 10

What test is used to measure for intellectual disability?

Answer 10

• Weschler Intelligence Scale for Children is an IQ test that estimates global intellectual ability and 4 composites (verbal, perceptual reasoning, working memory, and processing speed)
  
  • Limitations: low reliability w/ scores < 50; is culturally biased so results in lower scores in children that are culturally deprived

Question 11

When is intellectual disability usually diagnosed?

Answer 11

during school age years

Question 12

what is developmental delay?

Answer 12

• Developmental delay = delay in attainment of developmental milestones in children < 5yrs

doesn’t necessarily predict future intellectual disability

Question 13

What is Velocardiofacial Syndrome?

Answer 13

• Velocardiofacial Syndrome = caused by deletion of portion of Chromosome 22, characterized by developmental delay
  
  • delayed motor milestones, language delay, shyness, withdrawal, anxiety, difficulty w/ social interactions, disinhibition and impulsiveness

Question 14

What is neurofibromatosis Type 1?

Answer 14

• Neurofibromatosis Type 1 is an autosomal dominant disorder due to mutation in NF1 gene
  
  • characterized by café-au-lait macules, neurofibromas, optic glioma, learning disabilities (impaired visuospatial skills even though intelligence is in the lower range of normal)

Question 15

What is Noonan Syndrome?

Answer 15

• Noonan Syndrome = short stature, congenital heart disease, learning disabilities, dysmorphism; caused by mutation in RAS pathway
  
  • most have deficiencies in articulation that can be corrected w/ speech therapy