102. Intellectual Disability Flashcards
What is IQ?
What are the cut offs for Mild, Moderate, Severe, and Profound ID?
What percent of the population has ID?
IQ: Mental Age/Actual Age X 100
- normal distribution in general population, may not test all parts of intelligence
ID: IQ < 70
Mild: 50-70 (75% ID pts)
Moderate: 35-50 (20% ID)
Severe/Profound: 25-35/<25 (5% ID)
ID: 3% population - pts with severe disorders add extra 1% to the 2% of ID found in normal distribution
What are the four main etiologies of intellectual disability? Which are more common?
- Prenatal origin (most common)
- Chromosomal Abnormalities (most common)
- Single Gene Defects
- Malformational Sequences - Perinatal (2nd most common)
- Post Natal (infectious disease or brain injury)
- unknown
Fragile X Syndrome
- cause
- genetics
Single Gene defect on X Ch (XLR): FMR1 gene mutation of >200 CGG repeats in non-coding region (causes less gene product)
sx: testes enlargement during puberty and ID
premutation: 50-200 repeats; expand only in female meiosis
full mutation: >200 repeats (100% penetrance in males, 50% in females); expand in female meiosis and mitosis (mosaicism of extended repeats >200)
Transmitting Male: has premutation, but cannot expand it - his daughters will have same premutation, and will expand in her children causing some fully mutated males
Noonan Syndrome
- cause
- sx
AD, single gene defect
pectus excavation, webbed neck, close-set ears, ID
Incontinentia Pigmenti
- cause
- sx
XLD, lethal in males, single gene defect
mosaicism of rash -> hyperpigmentation in females (due to X-inactivation) and ID
Brachman-Delange Syndrome
- cause
- sx
Single Gene Defect (Nipped-B-Like Gene)
- defects in hands and lips
Difference in post-natal ID: deterioration and degeneration.
What is Familial ID?
Deterioration: injury from acute insult, IQ stabilizes after hit
Degeneration: steady decline of IQ over time (I Cell Disease for example)
Familial ID: IQ < 70 but non-pathologic, part of normal population spread
