Bullous delayed pressure urticaria; pressure testing may produce a systemic reaction

We report a patient with bullous delayed pressure urticaria (DPU) and chronic idiopathic urticaria (CIU) in whom a systemic reaction occurred. The reaction occurred 18 h after a pressure test had been performed on the right forearm. Blood histamine levels were more elevated in the sample taken from the forearm on which the test had be applied. Skin biopsy revealed both intraepidermal and subepidermal bullae with a sparse dermal inflammatory infiltrate and direct immunofluorescence showed linear deposition of fibrinogen along the epidermodermal basement membrane. As far as we are aware this is only the third case of bullous DPU reported and the first associated with generalized urticaria and angioedema and severe broncho-obstruction. Possible pathophysiological mechanisms are discussed.