A 3-year-old boy is brought to the child psychiatry clinic by his mother with concerns about his development. She reports that he speaks very few words, mostly echoing what others say. He does not make eye contact, prefers to play alone, and becomes distressed when his daily routine is changed—he insists on arranging his toys in a line for hours. On examination, he shows repetitive hand movements and does not respond to his name. His developmental milestones were normal until 18 months of age, after which his mother noticed a gradual loss of language and social skills. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis This case presents a clear picture of **Autism Spectrum Disorder (ASD) with regression**, a recognized variant within the current ASD diagnostic framework. ### Key Diagnostic Features Present **Social-Communication Deficits:** - Minimal speech with echolalia (repetition of others' words) - Absent eye contact - Preference for solitary play - No response to name **Restricted, Repetitive Behaviors:** - Lining up toys in a stereotyped manner - Repetitive hand movements (stimming) - Rigid adherence to routines with distress on change **Developmental Timeline:** - Normal development until 18 months - Subsequent loss of language and social skills (regression) ### Why This Is ASD with Regression, Not Childhood Disintegrative Disorder **Key Point:** Childhood Disintegrative Disorder (CDD) is now subsumed under ASD in DSM-5. CDD was historically defined as normal development for ≥2 years followed by regression before age 10. The current diagnostic framework recognizes regression as a **specifier within ASD** rather than a separate disorder. **High-Yield:** The DSM-5 (2013) consolidated CDD, Asperger syndrome, and PDD-NOS into a single Autism Spectrum Disorder diagnosis with severity levels and specifiers (including "with regression"). ### Differential Considerations | Feature | ASD with Regression | Intellectual Disability | Language Impairment | |---------|-------------------|----------------------|--------------------| | Social reciprocity | Markedly impaired | Variable | Relatively preserved | | Restricted interests | Present (stereotyped play) | Absent | Absent | | Repetitive behaviors | Prominent (hand movements, lining) | Absent | Absent | | Regression pattern | Can occur (18+ months) | Developmental plateau | Language plateau only | **Clinical Pearl:** Regression in ASD typically occurs between 12–36 months and affects both language and social domains. This child's loss of both skills, combined with the emergence of stereotyped behaviors, is pathognomonic for ASD. ### Diagnostic Criteria Met (DSM-5) 1. **Persistent deficits in social communication** (no eye contact, no response to name, solitary play) 2. **Restricted, repetitive patterns** (lining toys, hand movements, rigid routines) 3. **Symptoms present in early childhood** (onset by 18 months) 4. **Symptoms cause clinically significant impairment** **Mnemonic: ASD-R (Autism Spectrum Disorder—Regression)** = Social withdrawal + Language loss + Stereotypies + Onset in infancy/toddlerhood.