A person with a mycotic aneurysm has an aneurysm that is infected. Most mycotic aneurysms are caused by bacterial infections. This is a very serious infection that results in catastrophic bleeding or severe sepsis if it is not treated.

Less than 3% of all aortic aneurysms are a mycotic aneurysm.

There are two main kinds of mycotic aneurysms:

• Bacterial infection of the arterial wall leads to the formation of an aneurysm
• A pre-existing aneurysm in the wall of an artery becomes infected with bacteria.

They can occur:

• In the aorta
• In the femoral arteries
• In the mesenteric arteries
• In the carotid arteries
• In the iliac arteries
• In the cerebral arteries
• In the brachial arteries:
• Arteries in the upper arm
• In the left ventricle of the heart