A German scientist, Dr. Hans Asperger, described a milder form of autism that became known as Asperger syndrome. Thus these two disorders were described and are today listed in the Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR (fourth edition, text revision) 1 as two of the five pervasive developmental disorders (PDD), more often referred to today as autism spectrum disorders (ASD). All these disorders are characterized by varying degrees of impairment in communication skills, social interactions, and restricted, repetitive and stereotyped patterns of behavior.