A 75-year-old man presented to the emergency department with constant, unremitting vocal outbursts and confusion. The vocal outbursts had been present for the past 4 months and had progressively become more frequent over the past 24 hours. A consulting neurologist diagnosed Alzheimer disease accompanied with agitation/aggression and recommended an N-methyl-d-Aspartate (NMDA) receptor antagonist. A consulting psychiatrist diagnosed generalized anxiety disorder and recommended lorazepam, 0.5 mg every 12 hours, and quetiapine fumarate, 300 mg once daily at bedtime. The patient was discharged from the hospital to continue care with close monitoring at a nursing/rehabilitation facility.
Over the next week, the patient’s response to medical therapy was monitored. Despite improvement, his vocal outbursts returned at the beginning of the second week after discharge. Nursing staff at the rehabilitation facility reported that the outbursts returned abruptly within 12 hours of administration of a dose of lorazepam. What additional diagnosis might you consider?