Pustular drug eruptions: a histopathological spectrum.

We have reviewed the histopathological features of 11 patients with pustular drug eruptions. Two main histological patterns were seen. Eight cases revealed features of toxic pustuloderma with the presence of spongiform intraepidermal pustules in association with papillary oedema and a mixed inflammatory cell infiltrate around upper dermal blood vessels. Pustules were present at different levels within the epidermis. The other three cases exhibited leucocytoclastic vasculitis with neutrophil collections both below and within the epidermis. One case showed continuity between the subepidermal and intra-epidermal pustules. These findings suggest a dynamic process in which neutrophils collect around upper dermal blood vessels and are then eliminated via the overyling epidermis. The presence of extravasated red blood cells within the intra-epidermal pustules indicates that this process is passive rather than the result of specific chemotaxis or cell migration.