As someone with acute Exposure Anxiety as a major part of my autism, I was used to chemistry-driven involuntary avoidance, diversion, retaliation responses taking over my behaviour and communication whenever my adrenaline drenched over aroused emotional state triggered the fight/flight responses when others initiated and triggered my over sensitised 'invasion' alarm. This Exposure Anxiety (EA) was so severe and entrenched it developed to a secondary level so I not only was triggered into involuntary avoidance, diversion, retaliation responses when responding in fight/flight mode to the initiations of others but progressively also when I too desperately wanted to initiate something for myself- be that getting a drink, something to eat, going to the loo, getting a coat or taking one off, staying in a room or leaving it etc and I could usually do what I DIDN'T want to do at the time but generally not the thing I DID want to do. I found strategies around the EA rules of 'can't do it as myself', 'by myself' or 'for myself' (of course being prompted counts as 'doing as someone else' but doesn't lead to independence in EA) and how to use the yes=no/ no=yes mechanism to actually get relatively functional even if these strategies made me seem just as difficult to comprehend as the problem itself. (this is all written about in Exposure Anxiety; The Invisible Cage).
Recently, Chris and I visited two 'high functioning' friends diagnosed with ASD (diagnosed with Aspergers ). One of them also has Avoidant Personality Disorder. At a glance, on the surface AvPD looks a bit like EA, but where EA has nothing to do with confidence (one can be full of confidence and have severe EA), AvPD severely effects confidence. Where EA causes a range of involuntary behaviours, AvPD is a bit different. Where those with EA often desperately try to challenge the often impossible and self defeating confines of the invisible cage of EA (sometimes with self injurious results) , those with AvPD by it's nature may, through no fault of their own, be lacking motivation to challenge their condition. Though their behaviour often draws attention and is generally mistaken for attention seeking, EA is generally made worse through overt directly confrontational praise and encouragement and those with it are often most productive when there is no 'threat' of praise or attention (though they can constantly force others to prompt them). Those with AvPD, on the other hand, may need that encouragement constantly, even dependently.
What was interesting was that whilst AvPD isn't generally recognised until late childhood, it is possible that it goes overlooked or hidden in early childhood and it is fairly possible to imagine that misunderstood AvPD could compound the developmental and information processing issues inherent in autism. If this is so, its important to be informed about what it is so the right environmental approach can be used with those it most fits with. Something like ABA, for example, would likely need to be modified or exchanged for something more fitting where AvPD or EA compounded or underlie the person's autism. It's important that even though I have never had AvPD, to recognise that there is no one thing called autism and that understanding AvPD may hold some solutions for others. In case its of use to those others who may also have both AvPD and autism-spectrum condition, here's a link to a website with more info on it (albeit rife with words like 'disorder', 'abnormal' etc).