Mr. A, a 24-year-old man with a documented chromosomal abnormality of 48,XXYY evaluated by a standard cytogenetics technique, was admitted to the hospital for suicidal ideation and aggressive behavior toward his brother, whom he pushed down the stairs. He endorsed symptoms suggestive of a mixed bipolar episode before admission. He appeared to have borderline intelligence, with a documented IQ of 70–80, and was able to finish high school. There was no family history of psychiatric or genetic disorders. His physical appearance was notable for a tall stature, gynecomastia, and truncal obesity. His mental status examination was significant for irritability and a labile, intense affect. His cognition was intact. He had minimal insight into his illness.

Upon admission, Mr. A was given olanzapine and was later switched to oxcarbazepine and citalopram. Provisional diagnoses of bipolar disorder, not otherwise specified, and cluster B personality traits were made. Mr. A was initially uncooperative and frequently became agitated. Toward the end of admission, Mr. A seemed to respond to oxcarbazepine. His mood and behavior improved. He was discharged after 10 days of hospitalization with oxcarbazepine, 1200 mg/day, and citalopram, 40 mg/day.