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

INTRODUCTION: Biologic agents form an indispensable part of modern therapeutic regimens for the treatment of severe inflammatory diseases, especially in the fields of rheumatology, dermatology and gastroenterology. They are favoured by both physicians and patients due to their high effectiveness, good patient tolerance and safety. However, interference in the regulation and dynamics of inflammatory cytokines can on occasion lead to an onset of a dermatological condition also known as paradoxical skin reaction. Here, we present a case of paradoxical skin reaction induced by certolizumab. CASE REPORT: A young woman with ankylosing spondylitis developed a severe and complex cutaneous reaction after 6 months of otherwise successful treatment with certolizumab. The diagnosis of a rare paradoxical cutaneous reaction post anti-tumour necrosis factor alpha treatment was based on overlapping features of pyoderma gangrenosum and palmoplantar pustular psoriasis. Alopecia developed and there was also nail involvement. Treatment proved to be challenging as the disease did not remit after the patient ceased treatment with certolizumab. The patient was started on a combination of secukinumab and methotrexate to control the symptoms, with a promising outcome. CONCLUSION: Paradoxical skin reactions are an emerging clinical entity that require further research in order to establish risk factors and best personalized treatment.