Hyperkeratosis lenticularis perstans (Flegel's disease). In situ characterization of T cell subsets and Langerhans' cells.

We report a patient with hyperkeratosis lenticularis perstans (HLP) manifesting as multiple reddish-brown hyperkeratotic papules on the lower extremities. Typical histologic features of HLP include hyperkeratosis, thinning or absence of the granular layer and a band-like infiltrate in the upper dermis underlying an atrophic epidermis. In order to determine the cellular composition of the infiltrate, skin biopsy specimens were studied immunohistochemically using a series of commercially available monoclonal antibodies. The dermal infiltrate consists predominantly of helper/inducer T cells (Leu-4+, Leu-3a+). Suppressor/cytotoxic T cells (Leu-2a+) were fewer at the periphery of the infiltrate. The majority of T cells were activated as they expressed HLA-DR-antigen. Large numbers of Leu-6+ Langerhans' cells were observed at the dermo-epidermal interface. Few natural killer cells (Leu-11b+) were noted within the dermal infiltrate. These findings support the hypothesis than an active cellular immune reaction involving the epidermis is of pathogenic importance for HLP.