American Board of Internal Medicine (ABIM) Certification Practice Exam

Which condition is characterized by inflammation primarily affecting medium-sized arteries?

1. Granulomatosis with polyangiitis

2. Polyarteritis nodosa

3. Wegener's granulomatosis

4. Takayasu arteritis

The correct answer is: Polyarteritis nodosa

Polyarteritis nodosa is characterized by inflammation affecting primarily medium-sized arteries. This condition is a type of systemic vasculitis that involves the transmural inflammation of these arteries, leading to ischemia and potential aneurysm formation in the affected vessels. The pathophysiology involves an immune response that targets the walls of the arterial vessels, often triggered by viral infections or certain medications. In contrast, conditions like granulomatosis with polyangiitis and Wegener's granulomatosis are associated with small and medium-sized vasculature, but they are more characterized by granulomatous inflammation rather than the predominant involvement of medium-sized arteries seen in polyarteritis nodosa. Takayasu arteritis primarily affects large vessels, particularly the aorta and its major branches, rather than medium-sized arteries. Thus, polyarteritis nodosa is distinct as it specifically targets medium-sized arteries, making it the correct choice.