Autism Spectrum Disorders
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Group of neurodevelopmental disorders of early childhood:
- Includes autistic disorder, Rett syndrome, childhood disintegrative disorder, Asperger disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS)
- Autistic disorder includes classic autism and childhood autism.
- Rett syndrome involves mutations in the MECP2 gene, mostly in females with initial normal development until ~18 months of age with microcephaly and dementia.
- Childhood disintegrative disorder: Regression after at least 2 years of normal development.
- Asperger disorder: Better development with mechanics of verbal expression, higher levels of cognition and interest in social activity.
- PDD-NOS: Meets some, but not all of Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (Text Revision) DSM-IV-TR criteria for autistic disorder.
- Characterized by:
- Impairment of effective social skills
- Absent or impaired communication skills
- Repetitive and/or stereotyped behaviors and interests, especially in inanimate objects
- System(s) affected: Nervous
- NOTE: Proposed measurement changes in DSM-5, anticipated to come out in May 2013, extending the ASD diagnosis criteria which involve increased sensitivity to early childhood age of onset, as long as the “social demands exceed limited capacities.”)
- Predominant age: Onset in early childhood
- Predominant sex: Male > Female (4:1) except for Rett syndrome
Symptom onset seen in children <3 years (except for childhood disintegrative disorder)
Estimated 1/100 to 1/500 children
Siblings of affected children have a 5-times greater risk of developing autism. Prevalence ranging from 2–8%.Genetics
- High concordance in monozygotic twins
- Increased recurrence risk (3–7%) in subsequent siblings
- Early screening for early treatment means a better prognosis.
- Some autism spectrum disorders (ASDs) like Rett syndrome are caused by genetic mutations.
Pathophysiology is incompletely understood.
- No single cause has been identified.
- General consensus: A genetic abnormality leads to altered neurologic development.
- No scientific evidence relating vaccines, such as vaccines for measles, mumps, or rubella (MMR) (1), or thimerosal causing ASDs.
Commonly Associated Conditions
- Mental retardation
- Phenylketonuria (PKU), tuberous sclerosis, fragile X syndrome, Angelman syndrome, and fetal alcohol syndrome (rare)
- Obsessive behavior
- Seizures (increased risk if severe mental retardation)
- Maternal use of SSRIs during pregnancy (2)