Ruptured Syphilitic Aneurysm: A Cause of Sudden Death in a Man with Human Immunodeficiency Coinfection

Syphilis, a sexually transmitted infection caused by the bacteriumTreponema palladium, is experiencing a worldwide resur-gence. The risk of syphilis infection is particularly high in men who have sex with men (MSM), especially those who are human immunodefi-ciency virus (HIV)-positive. Untreated syphilis can lead to rare but severe late-stage complications, including syphilitic aortitis. Herein, wepresent an autopsy case of a ruptured thoracic aneurysm that resulted from an undetected case of syphilitic aortitis in an HIV-positive JapaneseMSM with undiagnosed syphilis. Although no syphilitic skin lesions were observed on the body, anatomical changes consistent with a syphili-tic 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 forT. palladiumin a latex agglutination test. This case highlights for forensic pathologists the importance of recogniz-ing syphilis as a possible underlying cause of sudden death among HIV-positive MSM.