What are the early signs of autism?

DEAR DOCTOR K: I've read that early treatment of autism can make a big difference. But what are the early signs of autism?
DEAR READER: You're right -- my colleagues who are experts in autism say that early recognition and treatment really can help. Autism (also called autism spectrum disorder, or ASD) is a developmental disorder of the brain. Kids and adults with autism have problems communicating and interacting socially. They also may have unusual behavior patterns, interests and activities. Symptoms range from mild to severe.