Infantile autism. Illustration of infantile autism also known as Kanner's syndrome. The main feature of this mental disorder is the child's inability to communicate by speech or to form abstract concepts. Autistic children have a preference to play alone and fail to form relationships. They may develop behavioural abnormalities such as sudden screaming, self injury and hyperactivity. Only about one sixth of autistic children have an independent life whereas the majority need special and continuos care. Autism is fortunately rare and affects about two to four children in every 10,000. Its precise cause is still unknown.