Answer by  
                                                                                          pmerc62 (7)
                                                            
                          
                          
                                                          Autism is actually a form of PDD, which I believe you are referring to.  PPD stands for "pervasive developmental disorder".  A person diagnosed with PDD may have difficulties in speech, any type of social interaction, repetitive/compulsive actions, etc.  However, a person with PDD may be considered to have a "high functioning" form of autism.