Paradoxical Skin Reaction to Certolizumab: Overlap of Pyoderma Gangrenosum and Psoriasis in a Young Woman Treated for Ankylosing Spondylitis - Case Report with Literature Review

A young woman with ankylosing spondylitis experienced a paradoxical skin reaction after 6 months of treatment with certolizumab, a biologic agent. This rare reaction manifested with symptoms of both pyoderma gangrenosum and palmoplantar pustular psoriasis, including alopecia and nail involvement. Despite discontinuing certolizumab, the condition did not improve, leading to the initiation of a combination therapy with secukinumab and methotrexate, which showed a promising outcome. This case highlights the need for further research into paradoxical skin reactions to biologic agents to better understand risk factors and develop personalized treatment strategies.