LAUSR

Syphilis, a sexually transmitted infection caused by the bacterium Treponema palladium, is experiencing a worldwide resurgence. The risk of syphilis infection is particularly high in men who have sex with men (MSM), especially those who are human immunodeficiency virus (HIV)‐positive. Untreated syphilis can lead to rare but severe late‐stage complications, including syphilitic aortitis. Herein, we present an autopsy case of a ruptured thoracic aneurysm that resulted from an undetected case of syphilitic aortitis in an HIV‐positive Japanese MSM with undiagnosed syphilis. Although no syphilitic skin lesions were observed on the body, anatomical changes consistent with a syphilitic etiology were present at the site of the rupture, including medial aortic scarring with “tree‐bark”‐like atherosclerotic plaque. In addition, heart blood was positive for T. palladium in a latex agglutination test. This case highlights for forensic pathologists the importance of recognizing syphilis as a possible underlying cause of sudden death among HIV‐positive MSM.