Asperger's Disorder must be distinguished from the other Pervasive Developmental Disorder, all of which are characterized by problems in social interaction.   It differs from Autistic Disorder in several ways.   In Autistic Disorder there are, by definition, significant abnormalities in the areas of social interaction, language, and play, whereas in Asperger's Disorder early cognitive and language skills are not delayed significantly.   Furthermore, in Autistic Disorder, restricted, repetitive, and stereotyped interests and activities are often characterized by the presence of motor mannerisms, preoccupation with parts of objects, rituals, and marked distress in change, whereas in Asperger's Disorder these are primarily observed in the all-encompassing pursuit of a circumscribed interest involving a topic to which the individual devotes inordinate amounts of time amassing information and facts.   Differentiation of the two conditions can be problematic in some cases.   In Autistic Disorder, typical social interaction patterns are marked by self-isolation or markedly rigid social approaches, whereas in Asperger's Disorder there may appear to be motivation for approaching others even though this is then done in a highly eccentric, one-sided, verbose, and insensitive manner.

      Asperger's Disorder must also be differentiated from Pervasive Developmental Disorders other than Autistic Disorder.   Rett's Disorder differs from Asperger's Disorder in its characteristic sex ratio and pattern of deficits.   Rett's Disorder has been diagnosed only in females, whereas Asperger's Disorder occurs much more frequently in males.   In Rett's Disorder, there is a characteristic pattern of head growth deceleration, loss of previously acquired purposeful hand skills, and the appearance of poorly coordinated gait or trunk movements.   Rett's Disorder is also associated with marked degrees of Mental Retardation and gross impairments in language and communication.

      Asperger's Disorder differs from Childhood Disintegrative Disorder, which has a distinctive pattern of developmental regression following at least 2 years of normal development.   Children with Childhood Disintegrative Disorder also display marked degrees of Mental Retardation and language impairment.   In contrast, in Asperger's Disorder there is no pattern of developmental regression and, by definition, no significant cognitive or language delays.

      Schizophrenia of childhood onset usually develops after years of normal, or near normal, development, and characteristic features of the disorder, including hallucinations, delusions, and disorganized speech, are present.   In Selective Mutism, the child usually exhibits appropriate communication skills in certain contexts and does not have the severe impairment in social interaction and the restricted patterns of behavior associated with Asperger's Disorder.   Conversely, individuals with Asperger's Disorder are typically verbose.  In Expressive Language Disorder and Mixed Receptive-Expressive Language Disorder, there is language impairment but no associated qualitative impairment in social interaction and restricted, repetitive, and stereotyped patterns of behavior.   Some individuals iwth Asperger's Disorder may exhibit behavioral patterns suggesting Obsessive-Compulsive Disorder, although special clinical attention should be given to the differentiation between preoccupations and activities in Asperger's Disorder and obsessions and compulsions in Obsessive-Compulsive Disorder.   In Asperger's Disorder these interests are the source of some apparent pleasure or comfort, whereas in Obsessive-Compulsive Disorder they are the source of anxiety.   Furthermore, Obsessive-Compulsive Disorder is typically not associated with the level of impairment in social interaction and social communication seen in Asperger's Disorder.

      The relationship between Asperger's Disorder and Schizoid Personality Disorder is unclear.   In general, the social difficulties in Asperger's Disorder are more severe and of earlier onset.   Although some individuals with Asperger's Disorder may experience heightened and debilitating anxiety in social settings as in Social Phobia or other Anxiety Disorders, the latter conditions are not characterized by pervasive impairments in social development or by the circumscribed interests typical of Asperger's Disorder.   Asperger's Disorder must be distinguished from normal social awkwardness and normal age-appropriate interests and hobbies.   In Asperger's Disorder, the social deficits are quite severe and the preoccupations are all-encompassing and interfere with the acquisition of basic skills.