S3239 Paradoxical Pustular Psoriasis Secondary to TNF Alpha Inhibitor Use in Ulcerative Colitis

Introduction: Infliximab is a tumor necrosis factor- alpha inhibitor (TNFi) used in moderate-severe ulcerative colitis (UC). It may also treat autoimmune conditions, such as recalcitrant psoriasis. However, TNFi may paradoxically cause new onset or worsening of psoriasis in ∼5% of cases. We present a rare case of TNFi induced psoriasis in controlled UC. Case Description/Methods: A 37 y.o M with pmhx of L-sided UC (2011) on infliximab 10mg/kg every 8wks (endoscopic Mayo Score 0, histological remission), ANA+, palmoplantar pustular psoriasis (2019, steroid responsive), and folliculitis presented to clinic for new rash. He reported 3 months of pruritic scalp and was diagnosed with seborrheic dermatitis with folliculitis. Ketoconazole, clobetasol, and doxycycline were prescribed. Of note, he was on infliximab for 10y and transitioned to a biosimilar formula 3mos prior. He re-presented a week later for progressive rash without infectious or systemic symptoms. Physical exam noted numerous erythematous non-follicular based papules with scaling and serosanguineous drainage (Figure 1a). Prednisone was initiated for concern of doxycycline drug reaction. Urgent dermatology evaluation revealed likely TNFi induced pustular psoriasis flare and worsening plaque psoriasis. Given response to steroids, a long taper was prescribed. Punch biopsy confirmed TNFi induced psoriasiform eruption (Figure 1b). As further TNFi was contraindicated, plan was to start ustekinumab. Discussion: TNFi may result in new onset or exacerbation of existing psoriasis in 5% of cases, which typically occurs within days to months of initiation. This is paradoxical in that TNFi may be used to treat psoriasis. The pathophysiology of TNFi induced and classic psoriasis differ as its immuno-footprint mimics early psoriasis via innate immune factor overexpression vs adaptive immune factor activation as in chronic disease. Though steroid responsive, TNFi are relatively contraindicated in TNFi induced psoriasis. Upon discontinuation, patients typically improve and may even tolerate future re-challenge. A prior case report also notes improvement of this condition with ustekinumab use, which our patient was transitioned to.Our case is unique in that TNFi induced psoriasis developed after transitioning to a biosimilar TNFi formula despite tolerating it for years prior. It also highlights a rare side effect of TNFi in controlled UC. It reinforces the importance of early clinical recognition and is an additional indication for close dermatology followup in UC.Figure 1.: A) Numerous erythematous non-follicular based papules with scaling and serosanguineous drainage in right axilla. B) Psoriasiform epidermal acanthosis with dilated capillaries in papillary dermis and lymphocytic inflammation, 10x H&E stain.