Sometimes things that seem off to parents about their child's behavior are developmentally appropriate. Find out what's typical, and when it's time to get help.

Dr. Paul Lipkin specializes in Neurodevelopmental Disabilities and Developmental and Behavioral Pediatrics at the Kennedy Krieger Institute in Baltimore, where he directs medical outpatient services.

Childhood disintegrative disorder (CDD) occurs when a child regresses in multiple areas of functioning after about 2 years of typical development. It is part of autism spectrum disorder (ASD).