An 83 year old man was admitted with a five month history of recurrent back pain, with no history of trauma. Episodic low grade fever, night sweats, loss of appetite, along with significant weight loss (about 10 kg over the past four months) were also reported. On examination, he appeared cachectic and unwell, presenting left flank tenderness without rebound. Apart from slight elevation of C reactive protein (9.4 mg/dL), no remarkable findings resulted from the blood chemistry. Ultrasound revealed a left retroperitoneal collection, better defined on computed tomography angiography (CTA) as a multiloculated psoas muscle collection with perivascular fistulisation to the terminal aorta and proximal left common iliac artery (LCIA) posterolateral wall. At this arterial level six mm diameter, 6 mm depth wall ulceration was visible (Fig. 1). Chest Xray and computed tomography (CT) scan were performed, revealing bilateral reticulonodular infiltrates in both lung fields. Sputum and blood cultures were negative as were immunological tests (anti-nuclear antibodies, anti-neutrophil cytoplasmic antibodies, rheumatoid factor, C3, C4 and immunoglobulins). Magnetic resonance imaging ruled out spondylodiscitis but documented the arterial wall involvement (Fig. 2). Percutaneous needle biopsy of the psoas collection was performed, under CT guidance. About 30 mL of a cheese like liquid was aspirated and sent to analysis. Both the acid fast bacillus test and the molecular test for Mycobacterium tuberculosis DNA were positive. The patient immediately started anti-tuberculous treatment (isoniazid, rifampicin, pyrazinamide, and ethambutol), and was discharged home after clinical improvement. He was compliant with medication and there were no side effects. During treatment he showed an impressive improvement of his clinical condition: fever remitted completely, he regained his body weight, and became functional and fully oriented. CTA follow up at three months showed complete resolution of the psoas collection with no changes in the known arterial ulceration. However, the six month CTA (Fig. 1) revealed ulceration evolution to a 40 mm pseudoaneurysm. The patient did not report any change in symptoms during this period. Despite his age, the patient was considered fit for surgery, and open repair was selected considering the infectious cause. Intra-operatively the pseudoaneurysm was excised revealing complete disruption of the terminal aorta and proximal left common iliac posterolateral wall (Fig. 3A). Surrounding tissues (caseous necrotic tissues and pus) were thoroughly debrided. An aorto-bi-iliac interposition graft was performed (16 x 8 mm silver acetate/triclosan collagen coated polyester graft Intergard Synergy  Getinge ) (Fig. 3B). The histopathological report of the aneurysm wall was caseating granulomatous inflammation consistent with tuberculosis infection. The M. tuberculosis DNA test was also positive in the tissues (aortic wall and adjacent soft tissues) that were collected intra-operatively. The post-operative course was uneventful. After consulting with the Infectious Diseases Department, it was decided to maintain oral anti-TB treatment for one year after intervention. After nine months the patient remained asymptomatic and positron emission tomography CT showed no pseudoaneurysm recurrence or signs suggestive of graft re-infection.