A 3-year-old boy is brought to the pediatric clinic by his mother with concerns about delayed speech and social withdrawal. She reports that he rarely makes eye contact, does not respond to his name, and prefers to play alone. On examination, he is observed lining up toy cars in a repetitive manner for extended periods and becomes distressed when the arrangement is disturbed. He shows no interest in interactive games and does not point to objects of interest. Developmental screening confirms significant delays in language and social reciprocity. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Autism Spectrum Disorder ### Key Diagnostic Features Present **Key Point:** The clinical presentation demonstrates the core diagnostic triad of autism spectrum disorder (ASD): impaired social interaction, deficient communication, and restricted/repetitive behaviors. ### Core Deficits Identified | Feature | Clinical Finding | ASD Criterion | |---------|------------------|---------------| | Social interaction | No eye contact, does not respond to name, plays alone | Persistent deficits in social reciprocity | | Communication | Delayed speech, no pointing to objects of interest | Deficits in nonverbal communication | | Restricted behaviors | Lining up toys repetitively, distress at disruption | Restricted, repetitive patterns of behavior | **High-Yield:** ASD diagnosis requires evidence of symptoms present from early childhood (typically manifest by age 3) and persistent across multiple contexts. This child meets criteria across all three domains. ### Differential Considerations **Clinical Pearl:** While intellectual disability may co-occur with ASD (in ~30% of cases), the specific pattern of social withdrawal with preserved motor skills and the presence of repetitive behaviors is characteristic of ASD rather than primary intellectual disability. **Mnemonic:** **SOCIAL** — **S**ocial reciprocity deficits, **O**bsessive repetitive behaviors, **C**ommunication delays, **I**mpaired joint attention, **A**ffective disconnect, **L**anguage pragmatics poor. ### Why ASD Over Language Impairment Specific Language Impairment (SLI) presents with isolated language delays but preserved social interaction and normal repetitive behaviors. This child's social withdrawal and stereotyped behaviors exceed what would be expected in SLI alone. [cite:DSM-5 Diagnostic and Statistical Manual of Mental Disorders]