Syphilitic descending aortic aneurysm presenting with characteristic double-ring sign on CT: Radiologic–pathologic correlation

A man in his 50s presented with worsening anterior chest pain. Serologic testing revealed active syphilis infection, and polymerase chain reaction testing was positive for COVID-19. Contrast-enhanced computed tomography demonstrated a descending thoracic aortic aneurysm with circumferential wall thickening and a characteristic double-ring sign suggestive of inflammatory aortitis. After blood pressure control and antibiotic therapy, elective descending aortic replacement was performed. Surgical inspection showed diffuse intimal thickening with a tree-bark appearance. Histopathology demonstrated lymphoplasmacytic infiltration in the media, adventitia, and around the vasa vasorum, consistent with syphilitic aortitis. This case highlights the diagnostic value of CT, particularly the double-ring sign, in identifying syphilitic aortitis and demonstrates a rare presentation of syphilitic aneurysm in the descending thoracic aorta.