P12 Paradoxal adalimumab induced palmoplantar pustulosis in a patient with Crohn’s disease

Abstract In November 2023, a 25-year-old man presented with pustular lesions on his palms and soles bilaterally. The pustules were sterile and the biopsy was compatible with psoriasiform dermatitis. In the following days, the patient developed erythematous, scaly, indurated, plaques on his trunk. From the clinicopathological correlation, the diagnosis was palmoplantar pustular psoriasis. The patient was under the treatment of adalimumab from the summer of 2021 for Crohn’s disease (40 mg/2 weeks, subcutaneously), until he proceeded to our clinic with palmoplantar pustulosis. Adalimumab was discontinued. The patient was treated with topical cortisone and keratolytics, in combination with ustekinumab for Crohn’s disease, with a gradual improvement of his symptoms. Tumour necrosis factor (TNF) is a pro-inflammatory cytokine. Adalimumab is a fully human immunoglobulin G1 antibody, blocking TNF activity. In our case, we have another paradoxical adverse reaction of adalimumab. Despite the effectiveness of adalimumab in the treatment of psoriasis and Crohn’s d, our patient developed palmoplantar pustular psoriasis, though he was under adalimumab for his Crohn’s d. Ustekinumab is a biological agent targeting interleukine-12 and 23 and is widely used in the management of both psoriasis and Crohn’s d. Our patient switched from adalimumab to ustekinumab, which kept his Crohn’s d stable and improved his palmoplantar pustular psoriasis, after 1 month