Ustekinumab (UST), a biologic agent targeting interleukin-12 and interleukin-23, is widely used in the management of psoriasis and Crohn’s disease. Despite its efficacy, there have been instances of paradoxical psoriasis induction or exacerbation in some patients during UST therapy. This paper offers a comprehensive review of reported cases of UST-induced paradoxical psoriasis, including a case from our clinic. We focus on a 39-year-old female patient with a history of long-standing Crohn’s disease who developed a psoriasiform rash, as confirmed by biopsy, while undergoing UST treatment. The patient’s clinical journey, from initial diagnosis through the complexities of treatment adjustments due to various complications including drug-induced lupus and the subsequent onset of psoriatic manifestations, provides insight into the challenges encountered in the clinical management of such cases. This review emphasizes the necessity for clinicians to recognize the possibility of paradoxical psoriasis in patients receiving UST treatment and calls for further research to better understand this phenomenon and devise effective management strategies.
