Blood Culture-Negative Cardiovascular Syphilis in an Untreated HIV-Positive Man

BACKGROUND Blood culture-negative endocarditis (BCNE) is an infection of the endothelium of the heart and valves with negative blood cultures. Cardiovascular syphilis is a late-stage presentation that typically involves the aorta and rarely affects the aortic valve. It is caused by the spirochete Treponema pallidum and is classified as a BCNE. The specific identification of T. pallidum as the causative pathogen in the heart requires next-generation sequencing on explanted tissue. Coinfection between individuals infected with human immunodeficiency virus (HIV) and syphilis is not uncommon. The effect of HIV positivity on the natural progression of syphilis is unknown, but the absence of antiretroviral therapy may be a risk factor for syphilis progression in individuals with HIV. Penicillin treatment for cardiovascular syphilis in individuals with untreated HIV should include the expanded antibiotic protocol for neurosyphilis. CASE REPORT A 44-year-old man presented with evidence of heart failure and untreated HIV. He had a history of noncompliance with healthcare and of partial treatment for syphilis 3 years prior to admission. A transesophageal echocardiogram revealed an aortic valve lesion, and his blood cultures were persistently negative. His rapid plasma reagin (RPR) was 1: 128, and he had active hepatitis C infection. He underwent aortic valve replacement. 16S rRNA sequencing of the aortic valve revealed T. pallidum. He was treated with penicillin and ceftriaxone and subsequently discharged. CONCLUSIONS Syphilis endocarditis is a rare and life-threatening diagnosis. This patient's HIV positivity and noncompliance with antiretroviral therapy likely accelerated the disease process and complicated his treatment course. The absence of aortic involvement with valvular syphilis is highly unusual.