Asperger’s disorder has several features that distinguish it from autistic disorder:
- Children with Asperger’s disorder do not have language delays. By definition, a child who has not developed single words by age 2 cannot be diagnosed with Asperger’s disorder.
- Early cognitive development in Asperger’s disorder is normal. Children with Asperger’s disorder are much more likely to have normal or above-average intellectual functioning than children with autistic disorder.
- Circumscribed interests and intense preoccupations are more common than motor stereotypies.
- Affected children may show verbal abilities that greatly exceed their visual-spatial skills. This may be apparent on individualized intelligence testing (i.e., verbal IQ > performance IQ) and clinically in the form of good language abilities but lagging fine-motor development (e.g., clumsiness).
Rett’s disorder occurs almost exclusively in girls, whereas autistic disorder is more common in boys. Following a brief period of normal development, affected girls experience deceleration of head growth, loss of previously acquired purposeful hand skills with subsequent development of stereotyped hand-wringing movements, loss of social engagement, onset of trunk and gait ataxia, and severe language and cognitive impairment. Genetic testing for mutations at MECP2 will be positive in most patients having all features of the classic phenotype.5
Childhood disintegrative disorder is thought to be more rare than autistic disorder. Following at least 2 years of normal development, affected children lose previously acquired skills. These can include play skills, language, social skills, bowel or bladder control, and motor skills. The children show impairments in social interaction, communication, and behavior of the type common to autistic disorder and often have severe mental retardation. The late onset of severe regression in development often prompts extensive neurologic evaluation, but a specific etiology is usually not found. The disorder is not diagnosed if full diagnostic criteria for autistic disorder are met (including onset of symptoms before age 3).
PDD NOS is diagnosed in many patients who are determined to have a significant impairment in social relatedness but do not meet full criteria for a specific PDD. Recent epidemiologic studies suggest that PDD NOS may be more common than autistic disorder.6 It may also be an appropriate designation for children with other proposed diagnostic constructs, such as nonverbal learning disabilities7 and multiple complex developmental disorders.8
Unfortunately, children diagnosed with PDD NOS instead of the better-recognized term “autism” may be denied appropriate social and financial services. When you inform others about the diagnosis of PDD NOS, it is important to emphasize to parents, schools, and funding agencies that PDD NOS is related to autism and should be considered one of the “autism spectrum disorders.” Children with PDDs or autism spectrum disorders will often benefit from similar treatment and educational interventions. In addition, their needs are equivalent for adequate insurance coverage and funding for specialized treatments.
- Cohen DJ, Volkmar FR (eds). Handbook of autism and pervasive developmental disorders (2nd ed). New York: Wiley, 1997.
- National Institute of Mental Health. Autism booklet. http://www.nimh.nih.gov/publicat/autism.cfm
- Autism Society of America http://www.autism-society.org Online Asperger Syndrome Information and Support (OASIS) http://www.udel.edu/bkirby/asperger