The authors emphasize that there are five specific autism spectrum diagnoses, or pervasive developmental disorders (the term used by DSM-IV-TR that is synonymous with autism spectrum disorders). These are autistic disorder, Asperger’s disorder, Rett’s disorder, childhood disintegrative disorder, and pervasive development disorder not otherwise specified. All of these disorders share certain features, such as deficits in reciprocal social interaction, deficits in communication, and restricted repetitive behaviors, interests, or activities. However, each of these disorders is different in some way. Children with Asperger’s syndrome have well-developed language and cognitive abilities. Rett’s disorder, in its classic and best-recognized form, is a rare behavioral syndrome found only in girls; female infants appear fine at birth and developmentally normal for at least 5 months or longer, but, within 6 months to a year, these girls lose use of their hands and lose interest in others and in social interaction. Childhood disintegrative disorder is a very rare condition that also involves a period of normal development of at least 2 years, followed by a loss of skills, resulting in severe impairments in cognitive, self-help, and other abilities. Although childhood disintegrative disorder can occur in either boys or girls, it is much more common in boys.