Autistic catatonia is an under recognised deterioration in motor function in autistic people, which most often occurs in adolescence. Catatonia has these features:
increased reliance on physical or verbal prompting by others
increased passivity and apparent lack of motivation
Parkinsonian features (e.g., freezing, excitement and agitation, a marked increase in repetitive and ritualistic behavior)
difficulty in initiating, completing, and inhibiting actions
If an autistic person you know has any of these characteristics and they are getting worse, they need intervention as soon as possible to limit and even reverse the deterioration. This can become very severe and even life threatening if it continues unchecked.
All of the characteristics listed refer to an increase in these characteristics. So, what if you or an autistic person you know has always been this way? Well, that would be considered just part of their autism rather than 'catatonia-like deterioration in autism', yet these problems are not known about, written about or talked about as part of autism. That is why I am interested in what autistic people call 'inertia' and finding out what relationship it has, if any, to the more pronounced and progressive catatonia. Chances are, inertia is more than one thing with more than one mechanism and I would venture that at least one of those is related to catatonia.