Understanding Autism Spectrum Disorders

A diagnosis of Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) serves as a kind of catch basin for the autism spectrum: If a child development expert does not see enough signs that fit into the diagnostic criteria for classic autism or Asperger's, for example, the child who has trouble with social interactions, communications skills, and demonstrates repetitive behaviors will be classified as PDD-NOS. The child could demonstrate problems in all three areas, but they appear less severe than children who receive a classic autism diagnosis.

A PDD-NOS diagnosis also can occur when a child is very young and a clearer picture has yet to emerge, or because the child is being diagnosed later than usual.

Some children who get this diagnosis when they are toddlers may have their diagnosis later changed or refined. That is why it is a good idea to monitor your child's progress over time and have autism specialists evaluate his behavior, social skills, and communication skills. (Read more about PDD-NOS.)

Childhood disintegrative disorder is a rare condition that resembles autism, but its onset occurs after a period of typical childhood development, usually two to four years.

The Developmental Disabilities Clinic at the Yale School of Medicine, a leading autism research center, notes that this disorder develops in children who previously appeared normal. "Typically language, interest in the social environment, and often toileting and self-care abilities are lost, and there may be a general loss of interest in the environment. The child usually comes to look very 'autistic,' i.e., the clinical presentation (but not the history) is then typical of a child with autism." (Click here to read more about childhood disintegration disorder.)