American Board of Pathology (ABPath) Practice Test

A mycotic aneurysm is specifically associated with an infectious process, typically resulting from a bacterial infection that weakens the arterial wall. The term "mycotic" originally referred to fungal infections, but it has evolved to include any infectious cause leading to aneurysm formation. In these cases, the infection can directly invade the vessel wall or result from septic emboli that originate from other infected sites in the body. This type of aneurysm often occurs in the context of endocarditis, where bacteria in the bloodstream can lodge in a blood vessel, compromising its integrity.

In contrast, dissecting, saccular, and fusiform aneurysms have more to do with structural issues related to the arterial wall, such as genetic factors, hypertension, or atherosclerosis, rather than infections. Dissecting aneurysms involve a tear in the vessel intima, allowing blood to flow between the layers of the vessel wall. Saccular aneurysms are sac-like outpouchings that typically arise at a specific point on the artery, while fusiform aneurysms involve diffuse, circumferential dilatation of the artery. These types do not have an infectious etiology and thus do not correspond to the answer.