Most autistic children are perfectly normal in appearance, but spend their time engaged in puzzling and disturbing behaviors which are markedly different from those of typical children. Less severe cases may be diagnosed with Pervasive Developmental Disorder (PDD) or with Asperger's Syndrome (these children typically have normal speech, but they have many "autistic" social and behavioral problems). Autism affects about 1 in every 150 kids, but no one knows what causes it. Some scientists think that some kids might be more likely to get autism because it or similar disorders run in their families. Knowing the exact cause of autism is hard because the human brain is very complicated.
A person with ASD may have difficulty empathising (understanding the thoughts and feelings of others or seeing the world from someone else's perspective). Because of this, they may sometimes make assumptions or say things which appear strange, rude or insensitive. It is very likely that it is not their intention to cause upset. Always stay positive with ASD children Being reliable is very important. Empathise with the issue that someone with ASD may be easily upset by unpredictable change and take simple steps to avoid this wherever possible (eg a post it note on a door to advise of a room change). If they say something that you would interpret as being rude, over familiar, or intrusive, be aware that they may not realise that their comment is inappropriate. Always get to know the individual first before communicating a certain way with them.