Introduction: 18q deletion syndrome is a rare genetic disorder characterized by various neurodevelopmental anomalies and medical issues. Although the occurrence of psychosis has been reported in a small number of cases, details regarding the nature of such symptoms and their response to treatment have not been described.

Case presentation: We describe a 31-year-old male with a history of speech delays, autistic features, a tethered spinal cord, bilateral vertical talus, subaortic stenosis and aortic regurgitation, recurrent otitis media, mild hearing loss, and hypospadias, who experienced a first episode of psychosis in his late 20s. His psychotic symptoms included auditory hallucinations, various delusions, and disorganization of thought. Although his presentation is atypical in certain ways (e.g., exhibiting highly fluctuant symptoms), he nonetheless meets criteria for schizophrenia. Given his overall clinical picture, chromosomal microarray analysis was completed, which revealed a 19.78 Mb deletion at 18q21.32 from nucleotide 58,226,713 to 78,015,180 (GRCh37). Despite exhibiting a somewhat idiosyncratic response to numerous antipsychotic medications, he eventually achieved partial remission of symptoms with improved insight on relatively low dose oral aripiprazole therapy.

Conclusion: This is the first in-depth description of 18q deletion syndrome-associated schizophrenia. While our patient's atypical presentation and idiosyncratic response to treatment may be mediated by his comorbid diagnosis of autism, his unusual psychiatric phenotype may alternatively be directly related to his underlying genetic disorder. The description of additional cases in the future will hopefully help clarify matters further.