Five conditions fall under the umbrella of autistic spectrum disorder:

Autistic Disorder, involves varying degrees of social and communication delays. Autistic children may avoid eye contact, speak little or not at all, and enjoy solitary, repetitive amusements. Some children may flap their hands or fingers or make other recurring body movements. Intelligence delays affect fewer than 50 percent of children with classic autistic disorder.

Asperger’s Syndrome, or “high-functioning autism,” is also marked by social and communication challenges and rigid routines or obsessive interests, but typically doesn’t involve intelligence or language delays.

Rett’s Syndrome, a rare condition that affects mostly girls, involving a lack or loss of speech, persistent hand wringing and a severe aversion to social contact.

Childhood Disintegrative Disorder, an extremely rare syndrome, in which mainly boys lose speech and social skills between the ages of two and four years old, after an otherwise normal childhood.

PDD-NOS (Persistent Developmental Disorder – Not Otherwise Specified), in which a child displays some autistic characteristics, such as social or verbal challenges, but doesn’t meet the standards for autistic disorder.