18F-Fluorodeoxyglucose Positron Emission Tomography/computed Tomography in the Diagnosis of a Rare Mycotic Aneurysm of the Thoracic Aorta in a Patient with Fever of Unknown Origin

Fever of unknown origin (FUO) is a condition with high mortality that often presents a diagnostic challenge to clinicians. We present the case of a patient with FUO who was discovered to have a rare mycotic aneurysm of the thoracic aorta by 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging. Mycotic aneurysm, also known as an infected aneurysm, is a highly lethal condition due to the risk of sepsis and aneurysmal rupture. While unusual to present in this manner, it is of utmost importance to promptly recognize a mycotic aneurysm as a potential diagnosis because initiation of treatment is critical in reversing the natural history of the disease.