Pigmented purpuric eruptions: immunopathologic studies supportive of a common immunophenotype

Traditionally, the pigmented purpuric eruptions (PPE) have been subdivided into four histologic categories, based upon variations in histologic pattern and clinical morphologies. In recent years, it has become apparent that the lesions behave similarly, and this family of eruptions has become grouped under the term PPE. The pathogenesis of these eruptions is largely unknown. In this study, we examined 13 examples of the histologic and clinical subtypes of the PPE with a panel of hematolymphoid immunophenotypic markers, in hopes of better understanding the pathogenesis of these curious eruptions. All lesions examined showed a predominantly T cell infiltrate composed of a mixture of OPD4 (CD4) positive and OPD4 negative cells. B cells were rare. Macrophages did not comprise a significant component of the infiltrate. The staining pattern was relatively constant, independent of the histologic pattern (i.e., Schamberg's vs. Gougerot‐Blum, etc) of the PPE. Our results suggest that PPE are a group of related eruptions which may have a common pathogenesis. It seems likely that the vascular damage and erythrocyte extravasation are secondary to a localized cell‐mediated immunologic event.