The three most common forms of Autism in the pre-2013 classification system were:
Autistic Disorder:  Classic Autism.
Asperger's Syndrome: Mild Autism
Pervasive Developmental Disorder:  Not Otherwise Specified (PDD-NOS).

These three disorders share many of the same symptoms, but they differ in their severity and impact.  
At times, Doctors unfamiliar with Autism still misdiagnose it for Bipolar. Make sure your Doctor is very familiar with both.