What are the symptoms of Autism Spectrum Disorder (ASD) in pediatric patients?

Symptoms of Autism Spectrum Disorder in Pediatric Patients

Autism Spectrum Disorder in children manifests through two core symptom domains: deficits in social communication and interaction, and restricted/repetitive behaviors, with most early warning signs becoming evident between 12 and 24 months of age. 1, 2

Core Diagnostic Features

Social Communication and Interaction Deficits

The social domain encompasses multiple impairments that distinguish ASD from typical development:

• Impaired nonverbal communication behaviors, including reduced eye contact, lack of pointing for interest (particularly notable at 20-42 months), and absence of conventional gestures at 20-42 months 1, 2
• Difficulty developing age-appropriate peer relationships, with children showing fewer nonverbal behaviors to initiate shared experiences 1
• Lack of social-emotional reciprocity, manifesting as reduced positive affect, higher negative affect, and lower sensitivity to social reward cues 1
• Deficits in joint attention, with significant differences in initiation of joint attention and requesting behaviors compared to typically developing children 1
• Failure to respond to name at 12 months, which is highly suggestive of developmental abnormality (86% of at-risk infants who fail to respond develop ASD or other developmental delays) 1
• Deficits in attention to voice at 24 months 2

Language and Communication Impairments

Language difficulties represent one of the most common presenting concerns:

• Delay in spoken language, affecting both verbal production and verbal comprehension, is one of the most frequent symptoms prompting initial medical consultation 3
• Language signs were present in 92.4% of cases in Italian cohort studies, making this one of the most represented categories of early signs 3
• Verbal skills are typically more impaired than nonverbal skills in classic ASD presentations 2
• Lack of imaginative play and reduced use of gestures in communication 4

Restricted and Repetitive Behaviors

This domain includes multiple manifestations that may emerge at varying timepoints:

• Stereotyped motor movements (stimming), including hand flapping, finger flicking, rocking, spinning, and atypical arm and foot movements during walking 5
• Atypical body movements that may emerge early or late during the second year of life 2, 5
• Repetitive behaviors with objects and body that are significantly higher in children with ASD compared to typically developing children 2, 5
• Insistence on sameness and difficulty with transitions 2
• Highly restricted interests of abnormal intensity 2
• Hyper- or hypo-reactivity to sensory input 2
• Atypical object use between 12 and 24 months 1

Developmental Timeline of Symptom Emergence

First Year (7-12 Months)

• First symptoms become evident in 41.9% of cases between 7 and 12 months 3
• Greater differences between ASD and typically developing children emerge at ages 12 months and 17 months 1
• Failure to respond to name at 12 months is a critical early marker 1

Second Year (13-24 Months)

• First symptoms appear in 27.6% of cases between 13 and 24 months 3
• Social interaction and relationships deficits were evident in 93.3% of cases by 24 months 3
• At 24 months, children later diagnosed with ASD demonstrate lower positive affect, higher negative affect, difficulty controlling behavior, and lower sensitivity to social reward cues 1
• ASD signs become obvious and pronounced in 5 of 7 items on communication and 5 of 20 items on socialization by 24 months 1

Behavioral and Emotional Regulation Symptoms

Beyond the core domains, children with ASD exhibit additional behavioral features:

• Difficulty controlling behavior and poor effortful emotion regulation 1
• Lower positive affect and higher negative affect compared to non-ASD siblings and controls 1
• Decreased IQ trajectory from average or near-average to more severe cognitive impairments in some cases 1
• Feeding problems are more numerous in cases with delay and stagnation of development 3

Cognitive and Functional Profile

The cognitive presentation varies widely but follows certain patterns:

• Approximately 30% of children with ASD have co-occurring intellectual disability, with 50% having severe to profound ID, 35% having mild to moderate ID, and 15-20% having IQ in the normal range 2
• Most individuals have average to above-average intellectual ability 2
• Cognitive level is the primary driver of behavioral presentation variability, more so than the core social communication deficits themselves 2
• Working memory and processing speed deficits are commonly observed 2
• Motor dysfunction may be evident in early developmental course 2

Common Co-occurring Medical and Psychiatric Conditions

Approximately 90% of children with ASD have at least one additional condition that affects symptom presentation:

• ADHD affects more than half of individuals with ASD 2
• Sleep difficulties affect more than half of children with ASD 2
• Gastrointestinal disorders affect around half 1, 2
• Epilepsy affects one-fifth to one-third, particularly those with co-occurring intellectual disability 1, 2
• Anxiety and phobias are common comorbidities 1, 2
• Depression occurs in approximately 20% of individuals with ASD compared to 7% in the general population 4
• Severe eating and feeding issues affect more than a third 1
• Irritability and challenging behavior affect around a fifth, including tantrums, self-injury, and aggression 1, 2

Modes of Onset

Three distinct patterns of symptom emergence have been identified:

• Delay in development: More frequent in patients with severe/profound intellectual disability, with motor skill disorders prevailing at onset 3
• Stagnation of development: More common in patients without intellectual disability 3
• Regression of development: More frequent in patients with severe/profound intellectual disability, with language signs at onset being less frequent in these cases 3

Critical Clinical Pitfalls

When evaluating for ASD symptoms, avoid these common errors:

• Do not adopt a "wait and see" approach when early warning signs are present, as early identification enables timely intervention with significantly improved developmental outcomes 2
• Do not assume all repetitive behaviors are simply autistic traits without screening for comorbid OCD, which requires specific treatment 2
• Do not overlook the need for comprehensive screening for ADHD, anxiety, depression, sleep disorders, gastrointestinal problems, and epilepsy, as these significantly impact function and quality of life 2
• Do not rely solely on language delay as a diagnostic marker, as it is common but not specific to ASD 3