A refractory Crohn's disease patient with recurrent perianal fistulas failed to overcome the secondary loss of response to infliximab (IFX) after therapeutic drug monitoring, intensified anti-TNF dosing and in combination with azathioprine. Throughout the treatment process, clinical pharmacists assisted physicians in analyzing the risk factors and causes for loss of response, providing evidence for an individualized treatment strategy, and monitoring the efficacy and safety of the treatment. According to the relevant guidelines and literature, ustekinumab was the preferred biological agent after anti-TNF failure in perianal fistulizing Crohn’s disease (pfCD). At the 12-week follow-up, fecal calprotectin and C-reactive protein decreased markedly, and the patient achieved fistula healing. This case provides references for current management strategy and perspective in IFX secondary non-responders with refractory pfCD, especially those who have undergone optimization therapy.

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