Upadacitinib-induced paradoxical face and scalp dermatitis: A case report of a novel sequela

Atopic dermatitis is a chronic, pruritic inflammatory cutaneous condition that can carry significant morbidity. Severe or recalcitrant atopic dermatitis is often treated with immunosuppressants, biologics, or immune-modulating small molecule therapies. The Janus kinase–signal transducer and activator of transcription pathway is highly implicated in atopic dermatitis pathogenesis, and agents that inhibit Janus kinase signalling are new to the atopic dermatitis landscape. Upadacitinib is a JAK1 inhibitor that has a good safety and efficacy profile and is increasingly being prescribed for atopic dermatitis. We report a case of a 35-year-old male with extensive atopic dermatitis that initially improved significantly on upadacitinib, then after 6 months developed a severe crusted dermatitic eruption on the head favouring a seborrheic distribution. While the pathogenesis of this paradoxical reaction is unclear, this phenomenon may involve a shift to a more Th1/Th17-mediated immune response.