Diagnostic Difficulties in Discriminating Autism Spectrum Disorder in an Adult With Periodic Psychosis Versus Schizophrenia Spectrum Condition: An Insight From Psychological Testing.

It has long been recognized that the biological underpinnings of autism spectrum disorder (ASD) and schizophrenia spectrum disorder (SSD) may share a common basis; however, the two conditions remain separate in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) due to a few distinguishing characteristics. Both disorders are characterized by cognitive and social deficits and have been presumed to be linked to multiple genes. We describe a 46-year-old male who presented atypically with three previous and one current episode of schizoaffective-like symptoms. We describe his previous inpatient admissions, current inpatient course, psychological test results, and treatment. The patient initially presented with schizoaffective disorder, but with a thorough interview, collateral information review, and psychological evaluation, it was determined that he instead was presenting with a previously undiagnosed case of ASD with brief psychosis when under stress. This case serves as an example of an atypical presentation of ASD which can be mistaken for schizoaffective disorder. It is important to establish the correct diagnosis, as the subsequent treatment and management of the patient's problems will depend on it. In such a patient, a low dose of atypical antipsychotic medication with serotonergic properties and psychotherapy would be the treatment of choice.