American Board of Psychiatry and Neurology (ABPN) Practice Exam

What is the most likely diagnosis for a 60-year-old man with confusion and inattentiveness over 5 days?

1. Depression

2. Dementia

3. Systemic lupus erythematosus

4. Delirium

The correct answer is: Delirium

The symptoms presented by the 60-year-old man—confusion and inattentiveness over a short duration of 5 days—are suggestive of delirium. Delirium is characterized by an acute onset of fluctuating consciousness and altered cognitive function. It often occurs in the context of underlying medical issues, such as infections, metabolic imbalances, or substance intoxication or withdrawal, and can develop over a very short time frame, typically hours to days. In this case, the acute presentation over five days supports the diagnosis of delirium, as patients usually display sudden changes in attention and cognition, distinguishing it from other cognitive disorders like dementia, which typically has a more insidious onset and gradual decline in cognitive function over months or years. Other conditions such as depression may also present with cognitive changes; however, the key feature of with depression is usually a lack of energy and a persistent low mood rather than acute confusion. Systemic lupus erythematosus can lead to cognitive changes as well but would typically involve additional systemic symptoms or laboratory abnormalities to warrant such a diagnosis. Since the symptoms are acute and align closely with the clinical picture of delirium, this is the most fitting diagnosis for the scenario described.