Pathological Demand Avoidance Syndrome (PDA) was first described in the 1980s in the UK, by Elizabeth Newson, and is an Autistic Spectrum Disorder related to, but significantly different from, 'standard' autism and Asperger's syndrome, and is increasingly becoming recognised as part of the autism spectrum. Recently (February 2017) there has been the change of language to PDA being a "profile within the autism spectrum"  and that is now reflected on the NAS website and in some supporting articles:
http://www.autism.org.uk/about/what-is/pda.aspx for more info.

Specifically, people with PDA will avoid demands made by others, due to their very sudden, and usually high, anxiety levels when they feel that they are not in control.

This PDA Resource website links to various recommended websites, Facebook pages, blogs, documents, graphics, & videos etc. and gathers together the best available information surrounding PDA, from sources around the world, to help parents, carers, professionals and others have a better understanding of PDA, and to provide help and support for people dealing with the condition.