Introduction

Prosthetic graft infection is a severe but rare complication of vascular surgery. In this case, we aim to show that not every abscess is a bacterial infection consequence and that it may be a side effect of immunotherapy.

Case Presentation

A 67-years-old man had undergone above-the-knee femoro-popliteal prosthetic graft bypass for chronic lower limb ischemia on AFS occlusion in October 2023. He has been treated by pembrolizumab as maintenance treatment for metastatic NSLC since August 2021, after primary lung surgery (right upper lobectomy) and radiotherapy of a frontal metastatic lesion, followed by wedge resection and right ribs resection (5th to 7th) in May 2019. He experienced cutaneous adverse reaction (pruritus) in May 2023, but the therapy was not discontinued. He recognized in November 2023 a subcutaneous lump and pain located in the bypass sites that gradually developed into a swelling subcutaneous mass. On physical examination the patient had a good general condition, a swollen growing lump under the site of the surgical incisions, that became inflamed in February 2024. Since the patient was apyretic, no antibiotics were administered. The CT scan showed the presence of well-incapsulated fluid collection around the vascular graft. We drained the collection, collected samples and performed a graft excision, tissue debridement and revascularisation with venous homograft. Cultures reported no bacterial growth.

Conclusion

In this case, the peri-graft abscess is observed as an immunological reaction to nonself-recognized foreign body following immune checkpoint inhibitor treatment.

Keywords: Vascular graft; Pembrolizumab; Immunotherapy-induced-abscess; Vascular surgery