Actinic lichen planus. A clinicopathologic study of 16 patients.

The clinical and histopathologic features of actinic lichen planus in 16 patients were studied. The majority of the patients were young, and men and women were almost equally affected. The relative incidence of this condition, compared with the incidence of all forms of lichen planus, was smaller than that reported in the literature. The eruption was distributed over sun-exposed areas, with particular predilection for the face. Covered areas and mucous membranes were spared except for one patient who had involvement of the vermilion border of the lower lip. In most cases the lesions consisted of erythematous brownish plaques with an annular configuration. Less commonly, discrete and confluent papules and hypermelanotic patches, sometimes assuming a melasma-like appearance, were present. The prominent histopathologic features consisted of an interface dermatitis characterized by coarse vacuolar degeneration of the basal cell layer, a mid-dermal perivascular predominantly lymphocytic inflammatory cell infiltrate, and a significant degree of pigment incontinence. Parakeratosis, eczematous changes confined to the follicular epithelium, and a variable degree of solar elastosis were seen in some patients. Mucin deposition was noted in the reticular dermis in two cases.