Atypical Autism: What the Term Meant and Where It Stands Now
Atypical autism was a diagnosis in ICD-10, the World Health Organization's classification system, for presentations that resembled autism but differed in age of onset or did not meet the full criteria. It was broadly the ICD equivalent of the DSM's PDD-NOS. ICD-11, effective 2022, removed it and folded these presentations into a single autism spectrum disorder diagnosis — matching the change the DSM-5 made in 2013. Existing diagnoses remain valid and no reassessment is required. If you were given this diagnosis, the current equivalent is autism spectrum disorder.
What it meant
ICD-10 listed atypical autism as a separate category from childhood autism. It applied where a presentation resembled autism but differed in one of two ways: onset appeared after the age of three, or the person did not show differences in all three areas the criteria required. In practice it functioned much as PDD-NOS did in the American system — the category for presentations that were clearly something, but didn't fit the criteria as written.
A note for readers outside the United States. ICD is the classification system used across most of the world, including the UK, Europe, and Australia. If you have an atypical autism diagnosis, it most likely came from an ICD-based assessment. American readers are more likely to have encountered PDD-NOS, which described a similar situation.
What changed
ICD-11 came into effect in 2022 and consolidated all previous autism subcategories — atypical autism, childhood autism, and Asperger's syndrome — into a single autism spectrum disorder diagnosis. It uses specifiers for intellectual functioning and language ability rather than separate categories. This aligned ICD with the DSM-5, which had made a comparable change in 2013, improving consistency in research and clinical practice internationally.
ICD-11 also added something the DSM-5 didn't: sensory processing differences appear in the diagnostic criteria for the first time in over 40 years, and loss of previously acquired skills is listed as a feature clinicians can use. Your diagnosis doesn't expire — existing diagnoses remain valid, and you don't need to be re-evaluated unless you want to, or unless a specific service requires a current-framework assessment.
Where sensory processing fits
ICD-11, which came into effect in 2022, formally includes sensory processing differences in the diagnostic criteria for autism — the first time sensory features have appeared in official criteria in more than 40 years. Assessments carried out under older frameworks did not evaluate sensory processing, because it wasn't a criterion. For many people it is the most persistent daily factor, and it is a legitimate thing to raise with an occupational therapist.
Browse verified occupational, physical, and speech therapy providers by city and state.
Browse the DrSensory Therapy Directory →Frequently asked questions
Is atypical autism still a diagnosis?
No. It was removed in ICD-11, effective 2022, and folded into autism spectrum disorder. Existing diagnoses remain valid and no reassessment is required.
What is atypical autism called now?
Autism spectrum disorder. ICD-11 uses a single diagnosis with specifiers for intellectual functioning and language ability rather than separate subcategories.
Is atypical autism milder than autism?
No. It described presentations that differed in onset or didn't meet all the criteria as written — not presentations that were less significant. Someone with an atypical autism diagnosis may have substantial support needs.
Is atypical autism the same as PDD-NOS?
They served similar functions in different systems. Atypical autism was the ICD-10 category; PDD-NOS was the DSM-IV equivalent. Both covered presentations that didn't fit the other categories, and both were retired.
Does my diagnosis still stand?
Yes. Existing diagnoses remain valid and don't expire. Re-evaluation is only needed if you want it or if a specific service requires a current-framework assessment.
References
- American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). APA Publishing. (DSM-5, published May 2013.)
- American Psychiatric Association. (2022). DSM-5-TR.
- World Health Organization. ICD-11 for Mortality and Morbidity Statistics (effective January 2022), 6A02 Autism spectrum disorder. icd.who.int
Medical disclaimer. This page is for general educational purposes and does not constitute medical advice, diagnosis, or treatment. Diagnostic terminology changes over time; a diagnosis you or your child received remains valid. Always consult a qualified healthcare provider about your individual situation.