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Medical Genetics > Autism and Dev Delay > Flashcards

Autism and Dev Delay Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Define the clinical definition of ASD

A
  • clinically heterogeneous group
  • complex behavior disorders that develop before 3yo
  • char by imparitment sin social interaction, communication, and repetitive behaviors
  • dx at age 2y –> reliable and stable
  • median age dx = 3y10m
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2
Q

What is current prevalence of autism?

A

1/150 in 2000-2002
1/68 in 2010-2012
1/59 = latest CDC stat
–> boys = 4x more likely

more than doubling now –> bc earlier age dx + including milder cases; not know if true occurrence is up

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3
Q

What percentage of those with autism have ID?

A

31%

(25% borderline, 44% average -above average)

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4
Q

What are some maternal exposures that can increase risk for autism?

A
  • maternal medications:
    valproate (seizure med)
    thalidomide (can treat leprosy or used in combo w other for mult myeloma)
    misoprostol
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5
Q

What are some prenatal infections that can increase risk for autism?

A

TORCH
Rubella

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6
Q

What is the breakdown of known causes for autism?

A

> 70% unknown
7-20% CNVs
5-7% Single-gene disorders
<5% Metabolic disorders

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7
Q

The spectrum of autism is comprised of what classifications?

A

idiopathic/isolated
- essential = no phys abnorma –> 70% cases
- complex = syndromic w dysmorphic features, major malform, and/or microcephaly –> 20-30% cases

secondary = cases where we can identify chromo abnorm, single-gene disorders, or environ agent

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8
Q

Incidence of autism is highest in what 2 genetic syndromes?

A
  • Down Syndrome –> 16.5%
  • 22q11.2 del syndrome –> 20%
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9
Q

What is the prevalence of Fragile X?

A

1/1000 males
1/700 females

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10
Q

Fragile X accounts for what percentage of X-linked ID and what percentage of autism?

A

25-50% X-linked ID
1-5% autism

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11
Q

What is the cause of Fragile X?

A

expanded CGG trinuc repeat (>200) in FMR1 gene on Xq27.3

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12
Q

What are clinical features of Fragile X in males?

A
  • slightly inc birth weight
  • macrocephaly
  • long face, large ears
  • macro-orchidism - post pubertal (large testes)
  • lax joints
  • MVP/Aortic dilation - post pubertal
  • DD/Autism –> 50-70%
  • periventricular heterotopia + other neuroradiologic abnorm

(bc expressed in brain + soft tissue & can cause conn tissue + GI symp)

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13
Q

What are clinical features of Fragile X in females?

A
  • prominent ears
  • long, narrow face
  • high arched palate
  • hyperextenisble joints
  • double-jointed thumbs
  • single palmar crease
  • flat feet
  • murmur or systolic click
  • milder dev symp
  • POI
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14
Q

What are the breakdowns of Fragile X for CGG repeats?

A

6-50 = normal allele (30=peak # in gen pop)
50-200 = premutation
>200 = full mutation

full mut –> the FMR1 protein NOT produced at all bc full mut = fully methylated

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15
Q

What are ways to diagnosed Fragile X?

A
  • order FX DNA test
  • PCR w CGG probe
  • Southern blot - digestion w EagI/EcoRI
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16
Q

What percent of autism is accounted for by Tub Scl?

A

1%

TS w SEGA (Subependymal giant cell astrocytoma (SEGA) brain tumor found in ~15% TS) have 2x risk of autism

17
Q

What are main findings in Rett syndrome?

A
  • normal dev from 6-12 months
  • pd of regression
  • loss hand movements
  • sizures
  • microcephaly
  • ID
  • Autistic features
  • hand-wringing; bruxism
  • hyperpnea; heart block
18
Q

What percent of autism is accounted for by Tub Scl?

A

~1% autism cases/4% females

19
Q

What is cause of Rett syndrome?

A

MeCP2 mut/del
CDKL5 –> atypical Rett

Males –> MeCP2 dup (otherwise lethal)

20
Q

What percent of autism is accounted for by NF1?

A

rare

  • common w ADHD and sometimes dev delay
21
Q

What is Phelan-McDermid Syndrome + its rln to autism?

A
  • microdel 22q13.3 (80%)
  • intragenic del of SHANK3
  • neonatal hypotonia
  • normal - accel growth
  • absent/v delayed speech
  • global dd
  • minor dysmorphic facial feat (Full brow, flat midface , ptosis, puffy eyelids, long eyelashes, wide nasal bridge, bulbous nose, puffy cheeks,
    pointed chin, large/prominent ears)
  • Autistic behaviors
  • mouthing non-food
  • dec pain perception
22
Q

What are some metabolic disorders associated with autism?

A
  • PKU (if untreated)
  • MPS III (Sanfilippo)
  • Adenylosuccinase def
  • Creatine def syndromes
  • Mito disorders (more likely in pts w these feat: lactic acidosis, episodic regression, hypotonia, optic nerve atrophy, diabetes, hearing loss)
23
Q

What percent of autism is accounted for by PTEN Hamartoma Tumor Syndrome?

A

1% autism cases
5% autism + macrocephaly

24
Q

What percent of autism is accounted for by CNVs?

A

Recent CMA studies revealed copy number variants in 7-20% of ASD cases

25
Q

What is the CMA diagnostic yield in patients w ASDs or ID?

A

15-20%

26
Q

What is the most common del/dup that accounts for autism?

A

16p11.2 –> accounts for 1.1-1.2% cases

27
Q

What was the main finding in “Rare CNV Variants in Autism Perturb Synaptogenesis”

A

they figured out that they can support hypoth that autism = mainly disease of synpatic + neuronal connectivity malfunction

28
Q

What was the main finding in “Genome-wide differential expression of synaptic long noncoding RNAs in autism spectrum disorder”

A

synaptic vesicle tranportation + cycling = imp in delivery of proteins to synapses in ASD

29
Q

What are some epigenetic factors linked to autism?

A

(thinking about changes in chromatin state that reg gene exp w/o changing DNA OG seq)

  • Rett syndrome –> MeCP2 gene binds to methylated DNA (so represses transcription of target genes)
  • imprinted regions, sucha s mat 15q13.3 microdup
30
Q

What is second tier w regard to testing autism according to ACMG?

A
  • MECP2 seq –> for all females w ASDs
  • MECP2 dup testing in males
  • PTEN testing only if head circumf is >2.5 SD above mean
  • Autism/ID panel (this is NOT pt of ACMG guidelines, but is realistic)
  • Brain MRI only if certain indicators (like microcephaly, seizures, etc)
31
Q

Among identical twins, if one child has ASD, then the other will be affected about ?% of the time

A

36-95%

32
Q

In non-identical twins, if one child has ASD, then the other is affected about ?% of the time

A

0-31%

33
Q

Parents who have a child with ASD have a ?% chance of having a second child who is also affected

A

10-15%

34
Q

If there are two affected siblings, the recurrence risk is approximately ?% if the subsequent child is boy and ?% if the child is a girl.

A

50% for boy
12% for girl

Medical Genetics (14 decks)

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