Autism is a brain disorder that affects the ability to communicate,
  socialize, sense the world, and to think. Each of these affects may be   mild or severe. The terms PDD (Pervasive Developmental Disorder)   and ASD (Autism Spectrum Disorder) both indicate the broad range
  of symptoms and severity that autism can have. Asperger's Syndrome,   usually characterized by higher functioning, is one part of the autism   spectrum.

  Some of the symptoms of autism are:

  · Odd play with toys - fascination with parts of toys like an   opening/closing door, spinning a toy, lining up the toys over and over,   won't play with balls.

  · Language problems - might not talk at all, echoes what he/she hears   from TV or others, won't ask questions, has problems using pronouns   correctly, talks mainly about his/her interests only, may not understand   voice tone and loudness, does not read body language or facial   expressions.

  ·  Changes are upsetting - surprises can cause extreme difficulties,   insists on routines, can cry or get upset for unknown reasons.

  ·  Sensory differences - may have little or no eye contact, may seem     deaf sometimes, uneven physical skills, fascinated with lights or   sounds, fearful of certain lights or sounds, unusual amount of physical   activity, extremely cautious or unusually fearless, may not want
  cuddling or hugging, different pain sensitivity.

  ·  Social differences - may avoid groups, difficult to make or keep   friends, treats people as objects, has difficulty understanding complex   emotions or motives, unable to lie.

  No one is sure what causes autism, but experts think it is a
  combination of genetic and environmental factors.