Lichen planoporitis: keratosis lichenoides chronica revisited.

We report a 70-year-old woman who over a 7-year period developed a widespread violaceous, reticulate and striate eruption with a keratotic component in a clinical pattern previously described as keratosis lichenoides chronica. Multiple biopsies showed a lichenoid reaction centred over the acrosyringium and eccrine ducts entering the epidermis. The acrosyringeal ducts were surrounded by an epidermis that was associated with saw-tooth acanthosis. The ducts displayed hypergranulosis and keratin plugs that extended into the stratum corneum. In the upper dermis the eccrine ducts showed squamous metaplasia with liquefaction of degeneration of their basal cells as well as apoptotic keratinocytes. The subepidermal acrosyringial zone and the eccrine ducts were associated with lymphocytic inflammation and fibrosis. These histopathological findings may represent the counterpart of lichen planopilaris targeting the eccrine ducts. The clinical features defining keratosis lichenoides chronica probably represents a heterogeneous group of conditions including this distinctive subset of lichen planus which we have termed lichen planoporitis.