A clinicopathologic study of scarring alopecia due to lichen planus: comparison with scarring alopecia in discoid lupus erythematosus and pseudopelade.

The clinicohistologic findings in 68 patients with lichen planus scarring alopecia (LP) were compared with those of 25 patients with discoid lupus erythematosus of the scalp (DLE) and 25 with pseudopelade (PP). The combination of diffuse scaling, erythema, telangiectases, and mottled hyperpigmentation within areas of scarring alopecia was a distinctive feature of DLE, whereas the clinical picture of PP was indistinguishable from that seen in 29 patients with LP. In most patients with LP, the histologic changes involved only the follicles and the perifollicular dermis. Less frequently, the inflammatory process extended to the epidermis and the papillary dermis. In all cases, histopathologic features allowed LP to be distinguished from DLE regardless of the stage of the disease. The finding of a bandlike fibrotic thickening of the papillary dermis accompanied by fibrotic tracts at sites of destroyed follicles appeared to be a hallmark of "burnt out" lesions of LP. This histologic clue may be helpful in achieving a specific diagnosis of LP in cases that fulfill the clinical criteria for PP.