Autism is a severe developmental disorder. The signs will show up anywhere from birth to within the first two-and-a-half years of life. Speech delay or communication disorders are a part of autism.
Although autistic children look perfectly normal in appearance, they may spend their time engaged in puzzling and/or disturbing behaviors which are markedly different from those of typical children.
Less severe cases may be diagnosed with Pervasive Developmental Disorder (PDD) or Asperger’s Syndrome (these children typically have normal speech, but have many “autistic” social and behavioral problems).
If you are not sure your child has an autism spectrum disorder, you should work with your child’s primary care physician to determine the best course for an evaluation. It is better to get evaluated as soon as possible if there are concerns.