Patients diagnosed as having KLC represent a potpourri of different diseases, the most common of them being lichen simplex chronicus, lichen planus, and lupus erythematosus. Some of the patients diagnosed with KLC, however, presented themselves in a manner very similar to one another and very different from the diseases just mentioned. The disease in those patients was widespread, lesions being situated on the face, extremities, especially the acral parts of them, the trunk less commonly, and, occasionally, mucous membranes. Individual papules were infundibulocentric and acrosyringocentric. Sometimes, papules had an atrophic center accompanied by tiny erosions or crusts. Also encountered often were comedo-like lesions. Keratotic papules and plaques could be discrete or, by way of confluence of them, form linear or netlike shapes. Findings histopathologic were those of a lichenoid dermatitis affiliated with numerous necrotic keratocytes and covered by parakeratosis and housing neutrophils in fashion staggered. The patients do not have lichen planus, lupus erythematosus, pityriasis lichenoides, pityriasis rubra pilaris, psoriasis, mycosis fungoides, or lichen simplex chronicus, but an authentic and distinctive condition that seems to be exceedingly rare. Cause and pathogenesis of it are not known, the course of the disease is protracted, and no treatment has been established for it. Retinoids and/or PUVA may serve to improve the condition in some patients.

In sum, the diagnosis KLC should be made only for patients who present themselves with features clinical and findings histopathologic that resemble closely those shown in our Category 3, to which the criteria for diagnosis forged in this article, both clinical and histopathologic, are applicable. It would be worthwhile for patients who conform to those criteria to be collected in an effort joint of colleagues to hone criteria for diagnosis and to determine, over time, the cause and pathogenesis of this distinctive condition.