A 3-year-old boy is brought to the paediatric clinic by his mother with concerns about delayed speech and social withdrawal. She reports that he does not point at objects to share interest, avoids eye contact, and prefers to play alone. On examination, he demonstrates repetitive hand-flapping movements and becomes distressed when his daily routine is altered. He lines up toys in a row rather than engaging in pretend play. His hearing is normal on audiometry. What is the most likely diagnosis?

Explanation

## Clinical Presentation This 3-year-old boy presents with the classic triad of impairments characteristic of Autism Spectrum Disorder (ASD): ### Core Diagnostic Features Present **Key Point:** The three core domains of ASD are: 1. Persistent deficits in social communication and interaction 2. Restricted, repetitive patterns of behaviour, interests, or activities 3. Symptoms present from early childhood (before age 3 in this case) ### Specific Findings Aligned with ASD Criteria | Feature | Finding in Case | ASD Criterion | |---------|-----------------|---------------| | Social reciprocity | No pointing to share interest, avoids eye contact | Deficient joint attention | | Social interaction | Prefers solitary play | Reduced social engagement | | Repetitive behaviour | Hand-flapping, lining toys in rows | Stereotyped motor movements | | Insistence on sameness | Distressed by routine changes | Inflexible adherence to routines | | Communication | Delayed speech | Pragmatic language deficit | **Clinical Pearl:** Joint attention deficits (failure to point to share interest, lack of gaze-following) are among the earliest and most specific markers of ASD, often evident by 12–18 months. **High-Yield:** The combination of: - Early age of onset (before 3 years) - Impaired joint attention and eye contact - Stereotyped repetitive behaviours - Preference for sameness - Normal hearing (rules out primary hearing loss) ...is pathognomonic for ASD. **Mnemonic: RIAS** — **R**epetitive behaviours, **I**mpaired social interaction, **A**bnormal communication, **S**ensory/restricted interests [cite:DSM-5 Diagnostic Criteria for Autism Spectrum Disorder]