Sweet's syndrome in the setting of newly initiated risankizumab therapy for pre-existing psoriasis.

Sweet's syndrome (acute febrile neutrophilic dermatosis) is a rare disorder of unclear aetiology characterised by painful cutaneous lesions, sometimes accompanied by systemic symptoms. It has been associated with several autoimmune conditions, drugs, malignancies and infections, though many cases are idiopathic. We describe a case of Sweet's syndrome in a 49-year-old man with pre-existing psoriasis following recent initiation of risankizumab therapy. There are very few reported cases of Sweet's syndrome in association with psoriasis and no existing reports in association with an IL-23 inhibiting medication. Further investigation of the potentially overlapping immunologic pathways implicated in cutaneous reactions to biologic agents and autoimmune conditions such as psoriasis may yield insights into the pathogenesis of such conditions and guide advancements in the rapidly evolving field of targeted biologic therapies.