OCD and autism do share some characteristics, so it is important to really investigate the diagnostic criteria of the disorders.
According to the DSM-IV-TR (2000), autism is characterized by significant impairment in social interaction (lack of appropriate emotional responses to events, such as not laughing at an event that most others would laugh at, or a lack of sharing enjoyment or interests with others), significant impairment in communication skills (delays in language development or the lack of make-believe or imaginative play), and repetitive and rigid patterns of behavior or interest (preoccupation with parts of objects or inflexible behavioral routines).
One of these impairments must develop prior to the age of three for the diagnosis of autism.
Autism’s delays in social development and language development are important to note; if a child is performing what appear to be rituals but also has delays in these areas, then autism is probably the appropriate diagnosis.
However, if there are no delays in language or socialization, then OCD may be the more accurate reason behind the behaviors.