So often we hear Autism Spectrum Disorder (ASD) generalized as autism, but what else is on the spectrum? ASD is considered a spectrum disorder because there is such an array of symptoms that can be demonstrated in several different ways with varying severity.

The American Psychiatric Association’s DSM (Diagnostic and Statistical Manual) for mental health disorders was first published in 1952. Since then, the definition of autism has changed. At first, autistic behaviors were associated with childhood schizophrenia. It wasn’t until 1980 and the third volume of the DSM that autism became listed as its own disorder.

When the fourth volume was released in 1994, there were four subcategories under autism and 16 different criteria for diagnosis. These four subcategories were Asperger’s Disorder, Rett’s Disorder, Childhood Disintegrative Disorder, and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS). Asperger’s became known as high-functioning autism. Rett’s and Childhood Disintegrative Disorders were used to describe children who began typically developing but then regressed, with autistic like symptoms. PDD-NOS became the catchall term for those who didn’t meet all of the criteria for autism, those who presented with atypical symptoms, or those who didn’t conform to a typical autism diagnosis.

In 2013, when the fifth volume of the DSM was released, all four subcategories were combined into a single label, Autism Spectrum Disorder (ASD). The removal of Asperger’s was controversial at the time. However, the umbrella label of ASD includes autism symptoms with or without intellectual disability, with or without language impairment, and with differing levels of severity.

What is Rett’s syndrome?

Rett’s syndrome is a genetic neurological disorder that leads to severe impairments. Mutations on the X chromosome cause it and occur almost entirely in females. The rare disorder affects 1 in 10,000 females. Like autism, Rett’s syndrome has a varying degree of severity, affecting speaking, eating, walking, and breathing. Rett’s syndrome is usually detected between 6 and 18 months due to missed developmental milestones or regression. One of the most easily identifiable characteristics of Rett syndrome is constant, repetitive hand movements. Other symptoms include:

Loss of speech
Loss of purposeful hands
Involuntary hand movements
Loss of mobility or gait disturbances
Loss of muscle tone
Seizures
Scoliosis
Breathing issues
Sleep disturbances
Slowed rate of growth for head, feet, and hands
A period of regression

There are four stages of Rett syndrome: Stage I is the early onset stage, occurring from 6 to 18 months. The second stage is the rapid destructive stage, which occurs from 1 to 4 years. Stage III is considered the plateau stage, occurring from preschool to adulthood. The final stage is the late motor deterioration stage, characterized by the loss of walking ability.

Rett’s is different from autism in a couple of ways. Children have autistic like symptoms at an early age, but they disappear as they develop. Certain symptoms do not occur in autism: reduced rate of head growth, loss of purposeful hands, loss of mobility, and irregular breathing. Another significant difference is that people with Rett syndrome tend to prefer other people over objects, and they enjoy affection.

What is Childhood Disintegrative Disorder?

Childhood Disintegrative Disorder (CDD), or Heller’s syndrome, is a developmental disorder in which children develop normally until 3 or 4 years old, and then they lose skills they have already learned. These skills include motor skills, language development, and social skills. The disorder is extremely rare, with 1 in 100,000 boys having it. CDD occurs 8 times more often in boys than in girls. The cause is unknown, but the neurobiology of the brain is suspected to be a contributing factor. Symptoms of this disorder include regression in the following areas:

Expressive or receptive language skills
Social skills
Self-care skills
Play skills
Motor skills
Bladder or bowel control

Other symptoms include:

Repetitive and restricted interests or behaviors
Two years of normal development
Gradual or rapid regression
Child’s awareness of regression
Emotional problems
Becoming averse to physical contact
Seem to be hallucinating
Fearfulness
Seizures

Compared to autism, childhood disintegrative disorder creates similar social and communication difficulties. The main difference is that there are usually 3-4 years of typical development, while those with autism begin missing milestones around 1.5 – 2 years. Epilepsy also occurs more often in Childhood Disintegrative Disorder than with autism.

Additional Resources

The CDC’s Developmental Milestone Checklist can be helpful in monitoring your child’s progress. Autism-Help.org has lots of information on Asperger’s and the other pervasive development disorders. Here is more information on Rett’s Syndrome. The CDC and National Institute of Health also have an abundance of information on ASD.

Tidy, C., Knott, L. (2021). Childhood Disintegrative Disorder. Patient Info. Retrieved from: https://patient.info/doctor/paediatrics/childhood-disintegrative-disorder-hellers-syndrome

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