littlelily613 wrote:
Also Rett's is no longer considered ASD, or at least it won't be when the DSM-V comes out. It is not being lumped into ASD, but is being removed entirely.
Yes, this, however, happened before. The term 'Autism spectrum disorders' used to encompass a group of disorders characterized by speech disorder, communication issues, stereotyped movements and, often, mental retardation manifested as IQ<70. Then, when the genes, defects in which were responsible for the respective disorders were identified, some small part of the ASD group was moved away to another category. This happened for Rett syndrome, Fragile X, tuberous sclerosis, even phenylketonuria, though the metabolic basis of the latter was discovered before Leo Kanner's first paper on autism was published. Such sub-categorization was done because they found that the genetic defect was responsible for more than ASD - as Rett's syndrome FraX and TS sufferers have numerous physical issues as well as autism-related trouble.
It is very difficult to set boundaries between disorders in real patients as their own genetic and metabolic makeup is a great phenotype modifier. That's why sometimes professionals depend on unusual crtiteria such as presence or absence of speech delay.
There is a subgroup of children, for an example, which at first receive a diagnosis of classic autism because of speech delay and all accompanying symptoms and some years later they are practically indistinguishable from some forms of Asperger's - special interests, subtle 'oddness', IQ>average, etc.
Also, in autism regressions are fairly common, so you might have a child without speech delay or even hyperlexic, who, however, lost early milestones, then gained them again, albeit slowly (so as to include CDD) and exhibited multiple sensory issues and needs to stim a lot, like in classic autism.
So unless you know that one started talking only at age 4, you wouldn't know what to put as a diagnosis.