Nummular dermatitis on guselkumab for palmoplantar psoriasis.

A 40-year-old man with chronic history of refractory palmoplantar psoriasis presented with new onset of well-demarcated oval erythematous asteatotic plaques on bilateral shins after starting guselkumab therapy. Histopathology revealed chronic spongiotic dermatitis consistent with a diagnosis of nummular dermatitis. This case highlights a previously unreported adverse event to guselkumab therapy.