Infliximab as ultima ratio in a case of refractory non-Crohn's disease complex fistula system: case report and mini-review of the literature.

Infliximab (IFX) has been a first-line treatment for perianal fistulizing Crohn's disease (CD) since 1999. However, its role in non-CD-related fistulas remains largely unknown, despite the established involvement of tumor necrosis factor (TNF) in both types of fistulas. A 76-year-old man with a history of prostate cancer presented in 2024 with recurrent fistulas and a presacral wound cavity with sepsis. He had been hospitalized approximately once a month over the past year due to fever and uncontrolled infection. The patient was initially treated with radiation in 2017. Despite this treatment, he developed increasing polyuria related to prostatic hyperplasia, which led to his first operation (prostatectomy) with accidental rectal injury, followed by multiple surgeries for complications and subsequent abscess formation. Histologically, there was no evidence of CD. Due to a lack of surgical options and failed endoscopic treatments, the patient was considered for exploratory IFX therapy. The patient received IFX induction therapy (5 mg/kg every 2 weeks for the first two doses) in May 2024, followed by maintenance therapy (5 mg/kg every 8 weeks). Within just 2 weeks, he reported the first significant clinical improvement. After 22 weeks of therapy with IFX, he reported feeling well, with no abdominal pain and a weight gain of 6 kg. At the 1-year follow-up, no further hospitalizations due to uncontrolled presacral infection with fever and anal pus discharge were reported, and the presacral wound cavity was found to be reduced on MRI from 37 mm × 43 mm × 62 mm (March 2024) to 23 mm × 22 mm × 45 mm (May 2025). Despite a history of recurrent urinary tract infections (UTIs) associated with mono-J catheters, the frequency of UTIs did not increase during therapy with IFX. This case indicates that infliximab may represent an effective therapeutic option for non-CD-related fistulas when there are no other therapeutic options available.