Asian Journal of Case Reports in Surgery

Introduction: Cardiovascular syphilis is an uncommon manifestation of tertiary syphilis in the antibiotic era. Although syphilitic aortitis predominantly involves the ascending thoracic aorta, isolated infrarenal abdominal aortic aneurysm (AAA) is exceptionally rare. Prompt diagnosis and combined medical and surgical treatment are essential to prevent life-threatening complications, including aneurysm rupture, aortic dissection and coronary ostial involvement.

Case Presentation: A 58-year-old normotensive, non-diabetic man presented with a progressively enlarging pulsatile abdominal mass associated with intermittent dull abdominal pain for five months. Physical examination revealed a non-tender pulsatile mass measuring approximately 5 × 5 cm in the umbilical and hypogastric regions. His blood pressure was 135/80 mmHg, without features of aortic regurgitation. Computed tomography angiography demonstrated a 7.5-cm infrarenal abdominal aortic aneurysm with right common iliac artery aneurysmal dilatation and adequate distal runoff. Serological testing revealed positive Venereal Disease Research Laboratory (VDRL) and Treponema pallidum haemagglutination assay (TPHA) results, with titres of 1:160 and 1:360, respectively. Neurological examination was normal, and transthoracic echocardiography showed a left ventricular ejection fraction of 65%, without aortic regurgitation or ascending aortic aneurysm. Chest radiography was unremarkable.

Following consultation with a dermatology and venereology specialist, the patient received intramuscular benzathine penicillin G (2.4 million units weekly for three weeks) before surgery. Open repair was subsequently performed using a 12-mm aortic limb and 6-mm iliac limb Dacron Y-graft. Total operative time was 150 minutes, infrarenal aortic cross-clamp time was 30 minutes, and estimated blood loss was approximately 500 mL. Gross examination of the excised aneurysm demonstrated the characteristic "tree-bark" appearance suggestive of syphilitic aortitis. The postoperative period was uneventful. The patient received heparin, ceftriaxone, metronidazole, amikacin, analgesics and supportive care. Doppler ultrasonography performed during six months of follow-up demonstrated satisfactory graft patency without vascular complications.

Conclusion: Syphilitic infrarenal abdominal aortic aneurysm is an exceptionally rare manifestation of tertiary syphilis. Positive serological tests, combined with characteristic operative findings, may strongly support the diagnosis when histopathological confirmation is limited. Preoperative antisyphilitic therapy followed by timely open surgical reconstruction can achieve favourable clinical outcomes. Clinicians should consider syphilitic aortitis in patients presenting with abdominal aortic aneurysms without conventional atherosclerotic risk factors, particularly in regions where syphilis remains prevalent.