• Autism
  • Pervasive Developmental Delay
  • Asperger's Syndrome

• Autism is a neuropsychiatric disorder that is diagnosed according to the behavior of the individual who has it; both the present behavior and the history of past behavior during growth and development lend weight to making the diagnosis.
• Autism falls into a wide spectrum of like behavior that is called, in children, "Pervasive Developmental Delay".
• There are variations in the spectrum of autistic behavior, some specific patterns have names - such as the verbal patients who are "higher functioning" and said to have Asperger's Syndrome.
• Whether all types of autistic behavior fall into one disorder, that has different levels of severity and variations in presentation- or more than one, is really not yet known.

As a matter of fact, it's hard to say whether autism is a single disease at all.

• In Medicine, a specific disease is something that has a single cause and understandable effect on the body.
  • For example, small pox infection,( which is hopefully now a disease of the past) was a disease that - no matter how awful in its effects, was understood.
  • The cause was infection with the small pox virus, and whether or not a person had the infection was something that could be proven- at least in facilities with adequate laboratories.
  • Autism is different. There is no gold standard test, no blood test or x-ray to confirm the diagnosis.

It's not that the diagnosis is arbitrary. The clinical picture of autistic behavior is distinctive enough that the diagnosis is likely to be given by disparate physicians who see the patient - but whether each and every person who is diagnosed with autism actually has exact the same biological disease is really not known. There may be more than one mechanism at work.

• In other words, in the disease small pox, affected people generally have a rash that looks a certain way, and a fever- but beyond this, tests for the presence of the small pox virus can be done to confirm the diagnosis.
• Not only are three separate doctors able to see the small pox patient, and make the same diagnosis (small pox) on the basis of clinical signs and symptoms, but there is a laboratory test to confirm this clinical diagnosis.
• In autism, the "clinical picture" is diagnostic, but there is no specific test that can be done to double-check this diagnosis and confirm that one child who fits the description has the exact same underlying cause of autism as the next.
• This means that each case of autism may not actually have the exact same underlying mechanism. Historically, this is a common situation with most diseases before the biological mechanism is understood and verified.

When it comes to this spectrum of Pervasive Developmental Delay, different names have been given to different patterns of behavior. Are these actually completely different disorders from each other? Are they related? These are questions that are being pursued by present research.

• NYU Child Study Center on Autism

• Autism in the Medline Plus Medical Encyclopedia

• Mayo Clinic on Autism

• Cleveland Clinic on Autism

• Understanding Autism
• Pervasive Developmental Disorder
• Asperger Syndrome