A 5-year-old girl is referred to the child psychiatry clinic by her school for evaluation of social difficulties and unusual behaviors. Teachers report that she does not interact with peers, prefers to sit alone, and becomes upset when classroom routines change. Her parents note that she has an intense, narrow interest in train schedules—she can recite entire timetables but shows little interest in other topics or play. She speaks in a formal, pedantic manner with unusual prosody. Her language development was on schedule, and she has no intellectual disability (IQ 115). She makes minimal eye contact and does not understand jokes or sarcasm. What is the most appropriate diagnostic formulation?

Explanation

## Diagnosis: Autism Spectrum Disorder, Level 1 (Requiring Support) ### Clinical Presentation Analysis **Key Point:** This case exemplifies autism spectrum disorder (ASD) in a child with average-to-above-average intelligence and no language delay—historically called "Asperger syndrome" or "high-functioning autism." The diagnosis is based on persistent deficits in social communication and restricted/repetitive behaviors, NOT intelligence level. ### DSM-5 Criteria Met | Criterion | Evidence in Case | Severity | |-----------|------------------|----------| | **Social-emotional reciprocity** | Does not interact with peers, sits alone, minimal eye contact, does not understand jokes/sarcasm | Moderate impairment | | **Nonverbal communication** | Unusual prosody, formal/pedantic speech, minimal eye contact | Moderate impairment | | **Relationships** | Prefers solitude, no peer interaction | Moderate impairment | | **Restricted interests** | Intense, narrow focus on train schedules; recites timetables | Restricted | | **Repetitive behaviors** | Distress with routine changes (insistence on sameness) | Restricted | | **Onset** | Early childhood (evident by school age) | Meets criterion | | **Functional impairment** | Social difficulties at school, limited peer interaction | Present | **High-Yield:** ASD is now diagnosed on a **spectrum with support levels** (DSM-5): - **Level 1 (Requiring support):** Noticeable difficulties in social communication or restricted/repetitive behaviors that interfere with functioning - **Level 2 (Requiring substantial support):** More marked deficits - **Level 3 (Requiring very substantial support):** Very marked deficits This child requires support for social communication and flexibility—fitting Level 1. ### Why Intelligence Does NOT Exclude ASD ```mermaid flowchart TD A[Child with average/above-average IQ]:::outcome --> B{Social-communicative deficits present?}:::decision B -->|Yes| C{Restricted/repetitive behaviors?}:::decision B -->|No| D[Not ASD] C -->|Yes| E[ASD diagnosis applies]:::action C -->|No| F[Not ASD] style E fill:#c8e6c9 ``` **Clinical Pearl:** ASD and intellectual disability are independent dimensions. A child can have: - ASD + intellectual disability (common) - ASD + average/above-average intelligence (this case) - Intellectual disability without ASD - Neither The presence of normal IQ does NOT rule out ASD; it only affects the severity rating and prognosis. ### Key Distinguishing Features from Comorbidities **Mnemonic: SARI** — **S**ocial deficits, **A**bsence of typical play, **R**estricted interests, **I**nsistence on sameness → ASD | Feature | ASD | Social Anxiety | OCD | Selective Mutism | |---------|-----|----------------|-----|------------------| | **Eye contact avoidance** | Qualitative difference; discomfort with social interaction | Anxiety-driven; wants to interact but fears judgment | Not primary | Not primary | | **Restricted interests** | Ego-syntonic; child enjoys them | Absent | Ego-dystonic; distressing to child | Absent | | **Insistence on sameness** | Core feature; distress if routines change | Absent | Present but linked to anxiety reduction | Absent | | **Humor/sarcasm** | Literal interpretation; difficulty with theory of mind | Understands but anxious in social contexts | Understands | Understands but may not express | | **Speech quality** | Atypical prosody, formal/pedantic | Normal prosody, anxiety-related hesitation | Normal | Selective silence | **Warning:** Do NOT confuse ASD with social anxiety disorder. A child with social anxiety WANTS to interact but is held back by fear; a child with ASD has a fundamental difference in social motivation and understanding, not just anxiety. ### Why Other Options Are Incorrect **High-Yield Distinction:** - **Social anxiety disorder:** Anxiety is the primary driver; the child wants social contact but fears judgment. This child shows a qualitative lack of interest in peers and difficulty understanding social cues—hallmarks of ASD, not anxiety. - **OCD:** While restricted interests and insistence on sameness can overlap with OCD, the child's interests are ego-syntonic (she enjoys train schedules) and her social deficits are primary, not secondary to compulsions. - **Selective mutism:** Involves refusal to speak in specific contexts due to anxiety, with normal speech elsewhere. This child speaks (albeit with unusual prosody) and has broader social-communicative deficits. [cite:DSM-5 Autism Spectrum Disorder; American Psychiatric Association 2013]