Thursday, February 26, 2009

Pervasive Developmental Disorder - Not Otherwise Specified

There is a new case that has hit the public awareness concerning one Bailey Banks who "suffered a seizure and Acute Disseminated Encephalomyelitis ('ADEM'), which led to Pervasive Developmental Delay 'PDD'." His case was somewhat recently (2007) decided by the special masters of the vaccine court in his favor and awarded compensation.

From the decision (page 27):
Based upon that finding of fact, it follows as a natural conclusion that Petitioner has carried his burden of proving to a preponderance that the MMR vaccine at issue actually caused the condition(s) from which Bailey suffered and continues to suffer. Inasmuch as the other elements of § 300aa–11 (b) and (c) have already been satisfied, the Court holds that Petitioner has met his burden on his case in chief.

These facts likewise satisfy the Althen test set forth above. Petitioner’s theory of PDD caused by vaccine-related ADEM causally connects the vaccination and the ultimate injury, and does so by explaining a logical sequence of cause and effect showing that the vaccination was the ultimate reason for the injury.
So the chain of events was MMR to ADEM which lead to PDD.

So, the question here is what is meant by PDD? A footnote on page 2 of the decision makes it clear that the term PDD is being used to refer to the child's diagnosis of PDD-NOS:
Pervasive Developmental Delay describes a class of conditions, and it is apparent from the record that the parties and the medical records are referring to Pervasive Developmental Disorder Not Otherwise Specified (“PDDNOS”) ... In the interest of consistency, the Court will follow the convention adhered to by the medical records and by the parties in this case, and this condition will be referred to herein as “PDD”.
So PDD is being used to represent PDD-NOS. So what is PDD-NOS? The decision also includes a reference to the definition from the Yale School of Medicine:
Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS) is a 'subthreshold' condition in which some - but not all - features of autism or another explicitly identified Pervasive Developmental Disorder are identified
So PDD-NOS is normally used to refer to people who have most but not all of the features of another form of PDD.  There are 5 subtypes of PDD : Autism, Asperger's, Rett's disorder, Childhood disintegrative disorder, and PDD-NOS.  Rett's has a known genetic cause and mainly affects girls and Childhood disintegrative disorder is very rare and doesn't apear until after 3-4 years old (whereas autism is always before 3).  I think we can safely eliminate Rett's and CDD from the discussion.   So that means that the PDD-NOS here is refering to a "subtreshhold" condition of either autism or aspergers.

Or in other words, the MMR lead to ADEM which lead to a form of autism.

Of course the reactions from the autism world have been quite heated as normal. The left wing started this whole debate with this post by Robert F Kennedy Jr and David Kirby in combination with a full page add in the USA today.  The right wing is of course attempting to highlight the use of PDD instead of the more specific term autism and to point out that the title of the decision is "Non-autistic developmental delay".

So, what to make of all of this?

First, PDD-NOS is normally considered a diagnosis that falls on the autism spectrum. This is the official diagnosis that my children have and they are considered as having autism. So saying PDD-NOS is, under normal conditions, the same as saying a form of autism.

But the title makes it clear this this is supposed to be a "Non-autistic developmental delay" so how can we reconcile between the normal usage of PDD-NOS and the distrinction used here?  I think an answer to this deiliema can be found on page 7 of the decision :
Moving on to the alternative hypothesis/diagnosis of autism, Dr. Lopez distinguishes autism as a more generalized condition without a known etiology, and contrasted it to Bailey’s condition, which he says is clearly attributable to demyelination based on neuroimaging evidence.
In other words, it isn't autism because we know what caused it.  Or what is more likely the case, we won't call it autism because  we know a vaccine caused it.

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