Autism

Neurodevelopmental Disorders & Learning Differences

Atypical Autism (PDD-NOS): Symptoms, Diagnosis & Support Before DSM-5

Authored by: The DrSensory Editorial Team

Reviewed by: 🛡️ DrSensory Clinical Review Board

Last updated: June 2025

All medical content on this page has been reviewed and approved by licensed Doctors on the DrSensory Clinical Review Board. Our reviewers follow strict editorial standards and ensure alignment with current APTA guidelines, evidence-based practice, and orthopedic rehabilitation protocols.

What is Atypical Autism and how was it diagnosed before the DSM-5?

Atypical Autism was a diagnostic term used in the DSM-IV and ICD-10 to describe individuals who displayed some—but not all—of the typical features of autism. Also called Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS), this diagnosis was used when autism-like symptoms were present but didn’t fully meet the criteria for Classic Autism or Asperger’s Syndrome.

Atypical Autism typically involved:

  • Delayed or unusual social and communication skills
  • Repetitive behaviors or restricted interests
  • Milder or later-onset symptoms

Since 2013, the DSM-5 has replaced Atypical Autism with a broader Autism Spectrum Disorder (ASD) diagnosis that includes all prior subtypes.

What are the symptoms of Atypical Autism (PDD-NOS)?

Symptoms of Atypical Autism vary widely but may include:

  • Difficulty with social interaction (e.g., trouble understanding social cues)
  • Speech or language delays, but not as severe as in classic autism
  • Repetitive behaviors, routines, or focused interests
  • Milder sensory sensitivities or emotional dysregulation
  • Symptoms that appear later than age 3

Because symptoms were often less intense or inconsistent with strict autism criteria, children diagnosed with PDD-NOS were sometimes described as having “subthreshold” autism or “mild autism.”

How is Atypical Autism different from Classic Autism or Asperger’s Syndrome?

Atypical Autism sits between Classic Autism and Asperger’s on the former diagnostic spectrum. Unlike Classic Autism, individuals with Atypical Autism often had:

  • Later onset of symptoms
  • Less severe communication delays
  • Variable presentation of social or behavioral challenges

Compared to Asperger’s, Atypical Autism typically involved:

  • More noticeable speech or developmental delays
  • Greater difficulty in adaptive functioning
  • Broader variance in severity and behavior

In today’s terms, people once diagnosed with Atypical Autism would likely fall under ASD Level 1 or 2, depending on their support needs.

How is Atypical Autism treated and supported today?

While Atypical Autism is no longer an official diagnosis, individuals with these traits receive the same evidence-based support used for Autism Spectrum Disorder (ASD) today. Treatment plans often include:

  • Speech and language therapy for communication skills
  • Occupational therapy to improve sensory processing and motor skills
  • Behavioral therapy, such as Applied Behavior Analysis (ABA)
  • Social skills training to aid interaction and emotional regulation
  • Individualized Education Plans (IEPs) in schools

Early diagnosis and personalized therapy are key to helping individuals build independence and thrive socially and academically.

This page provides general educational content and is not a substitute for professional medical advice. Always consult a licensed provider for diagnosis and treatment.

View privacy policy, copyright and trust info

Therapist Ratings & Reviews

Find a Therapist near you

Are you looking for a physical, occupational, or speech therapist in your area?
Look no further than the DrSensory Therapist Database and Clinic Directory!

What Are Others Reading?

Got Concerns?

Find a Therapist

Find the physical therapist, occupational therapist, or speech language pathologist you’re looking for!

Ask Us Anything

Whether you are looking for advice, have a general question about sensory processing, or looking for resources.

Submit Your Story

Share your story about your child. Let’s celebrate milestones and learn more about challenges.

Therapists and Clinics Near You!