Definition
- Autism spectrum disorder (ASD) is the consolidation of autistic disorder, Asperger’s disorder, and pervasive developmental disorder, representing a single continuum of mild to severe deficits in social communication and restrictive repetitive behaviors/interests
- Encompasses disorders previously referred to as early infantile autism, childhood autism, Kanner’s autism, high-functioning autism, atypical autism, pervasive developmental disorder not otherwise specified, childhood disintegrative disorder and Asperger’s disorder
- A neurodevelopmental disorder that begins in childhood that involves:
- Persistently impaired social interaction
- Persistently impaired reciprocal communication
- Presence of restricted and repetitive patterns of behaviors, interests or activities
- Presence of symptoms from early childhood
- Limited or impaired everyday functioning
Signs and Symptoms
Deficit in Social Skills
- Abnormal eye contact
- Failure to orient to name
- Failure to use gestures to point or show
- Lack of interactive play
- Failure to make appropriate social smile
- Lack of sharing of emotion or interest
- Lack of interest in other children
- Often withdrawn and spends hours in solitary play with restrictive or repetitive interests and behaviors
Impaired Social Interaction
- Impairment in joint attention - ability to use eye contact and pointing for the purpose of sharing experiences with others
- Deficits in empathy for what another person might be feeling
- Deficits in understanding what another person might be thinking
Deficit in Language and Communication
- Nonverbal that ranges from minimal vocalization to having some speech (eg capable of imitating songs, rhymes, or television commercials)
- Odd prosody or intonation of speech
- Echolalia
- Pronoun reversal
- Nonsense rhyming
- Other idiosyncratic language forms
Aberrant Play Skills
- Little symbolic play
- Ritualistic and rigid behavior, needs to maintain a consistent, predictable environment
- Tantrum-like rages when routines are disturbed
- Preoccupation with parts of objects
Restricted, Repetitive Behaviors, Interests or Activities
- Stereotyped or repetitive motor movements (eg lining up objects, flipping objects)
- Insistence on sameness, inflexible adherence to routines or other rituals
- Highly restricted, fixated interests
Variations in Intellectual Functioning
- Mental retardation to superior intellectual functioning in select areas (splinter skills, savant behavior)
- Typical development in certain skills and can even show strength in specific areas, such as puzzles, art, or music
Heightened Awareness to Stimuli
- Visual scanning of hand and finger movements
- Mouthing of objects
- Rubbing of surfaces
Lowered Sensitivity to Stimuli
- Diminished response to pain
- Lack of startle response to sudden loud noises
Pathogenesis
Genetic Factors
- Brain development alteration specifically neural connectivity which affects social communication development and resulting to restricted interests and repetitive behaviors
- It has been proposed that interactions between multiple genes or gene combinations are responsible for ASD and that exposure to environmental modifiers help contribute to variable gene expression
Neurobiologic Factors
- Atypical neural connectivity as a result of abnormal neuronal differentiation during prenatal development contribute to the development of ASD
Parenteral Age
- Advanced paternal or maternal age have been postulated to cause de novo spontaneous mutations and/or genetic imprinting alterations leading to development of ASD
Environmental and Perinatal Factors
- Eg exposure to toxins or teratogens, perinatal insults, prenatal infections (eg rubella, cytomegalovirus)
- Effect depends on timing and duration of exposure, toxin concentration, mechanism of action and distribution in the central nervous system
- Modulate existing genetic factors predisposing to ASD
Epidemiology
- Prevalence rate of ≥1% in children and young individuals
- One in 36 children aged 8 years across the United States has been identified with ASD in 2020
- More frequent in boys
- Estimated prevalence rate in siblings of a child with ASD is 10%
- ≥1% of children have regression or stasis of language and social behavior, usually occurring between ages 1 and 2 years
Risk Factors
- Risk factors include advanced parental age, prematurity, neonatal encephalopathy and genetic vulnerability