Differences in extracellular matrix proteins, epidermal growth and differentiation in discoid lupus erythematosus, lichen planus and the overlap syndrome.

Lichen planus (LP) and discoid lupus erythematosus (DLE) are separate disease entities. Nevertheless, patients with a so-called "overlap syndrome" have been described occasionally. The aim of the present study was to establish whether the LE/LP overlap syndrome, based on clinical and routine histological features, could be delineated from DLE or LP using immunohistochemical techniques. Formalin-fixated, paraffin-embedded skin biopsies of patients with DLE, LP and the overlap syndrome were compared regarding immunohistochemical markers for epidermal growth and differentiation and extracellular matrix components. With the markers for extracellular matrix proteins, it was possible to delineate the overlap syndrome from LP. This was not possible for the overlap syndrome and DLE. These findings might indicate that the LE/LP overlap syndrome could be considered as LP-like DLE rather than as a distinct disease entity.