C9orf72 and behavioral variant of frontotemporal dementia: Though infrequently used in clinical practice, genetic testing can identify mutations linked to neurodegenerative diseases associated with psychosis.27 For example, hexanucleotide repeat expansions caused by chromosome 9 open reading frame 72 (C9orf72) mutations are the most common genetic abnormality in behavioral variant frontotemporal dementia (bvFTD) and familial amyotrophic lateral sclerosis (ALS) and are associated with an increased risk for psychosis.43,44 A thorough interview, inquiring about family history of neurodegenerative diseases, is also important to identify genetic causes.27