The obsessiveness and rigidity in those two disorders, though, come from two different places. In Obsessive Compulsive Personality Disorder (OCPD), it's an attempt to control one's environment in order to contain the anxiety, remain clean, etc. In developmental disorders, it comes from not understanding one's environment and being able to process all the stimuli, struggling with complex processes, etc. In the latter, those things can create anxiety. In the former, it's done to contain anxiety.