I havn't had expérience regarding this disorder itself,however i can tell you that genetically there are no clear lines between ppd,schizoaffective disorder and schizophrenia.
In addition,Schizophrenia and Autism has also been found to have overlapping genes.
Unfortunately,most doctors have fallen into the pattern of labelling/ginseng labels,rather than on person centred treatment.
This ends up in a person receiving different labels,depending on which Psychiatrist they see and that Psych's point of view,and often little or no effective treatment.
Your son may benefit from Cognitive remediation with a Psychologist but this is rare in Australia.
He might be able to achieve some success with changing his cognition and how he interprets certain events or peoples actions.
It would have to be with someone he likes and trusts though.
http://m.apt.rcpsych.org/content/15/1/40.fullWhat is your sons opinion regarding receiving this diagnosis?