Bullous delayed pressure urticaria: pathogenic role for eosinophilic granulocytes?

Bullous delayed pressure urticaria (DPU) is a rare variant of DPU. Treatment of DPU is difficult and the underlying pathogenic mechanism of DPU remains elusive. We report a 72-year-old man with DPU and associated chronic urticaria as well as delayed urticarial dermographism. Pressure challenge gave rise to a deep weal covered by multiple vesicles and bullae after 24 h. Histological examination of a skin biopsy specimen obtained 24 h after pressure challenge demonstrated intraepidermal bullae filled with eosinophils accompanied by a dense, predominantly eosinophilic infiltrate in the dermis. Whereas the numbers and morphology of mast cells were unaltered, the extracellular deposition of eosinophil cationic protein revealed evidence for eosinophil activation. Concomitantly, both CD4+ and CD8+ T lymphocytes were present in the infiltrate and expressed interleukin 5. As bullous DPU may represent the maximal variant of DPU, the investigation of the cellular infiltrate and the chemokines/cytokines released may reveal potential pathogenic mechanisms. A possible effector role of eosinophilic granulocytes, T-cell subsets and mast cells is discussed.