In order to forge criteria that are repeatable for diagnosis of KLC, it seems essential to focus on those 24 patients who, based on the attributes pictured in articles, presented themselves with lesions very similar to each other. If one concentrates on those patients only and compares features clinical and findings histopathologic in them, the aspects in common are as follows:

Age and sex: Men and women are affected equally, all patients being adults.

Distribution of lesions: Face, extremities, especially acral parts of them, the trunk less commonly. Mucous membranes said to be affected in one fourth of the patients.

Arrangement of lesions: Widespread.

Configuration of lesions: Discrete as well as linear, arcuate, netlike as a consequence of confluence of papules. Lesions may assume shapes that look artificial by virtue of a Koebner phenomenon.

Individual lesions: Papules infundibulocentric and papules around acrosyringia, comedo-like lesions, atrophic papules with tiny erosions or crusts in the center of them, keratotic papules and plaques.

Symptoms: Pruritus is a finding inconsistent, it being present in less than 20% of the patients.

Course: The course is protracted. Resolution complete has never been reported. Patients tell of having had lesions for years before the diagnosis was made correctly.

Lichen planopilaris: In both KLC and lichen planopilaris, lesions are infundibulocentric papules, some of which may be typified by a keratotic plug in the center of them, but patients with lichen planopilaris often present themselves with scarring alopecia, a feature never encountered in KLC.

Pityriasis rubra pilaris: Pityriasis rubra pilaris as well as KLC are typified by infundibulocentric papules, but in pityriasis rubra pilaris those are joined by interinfundibular papules and, moreover, lesions often become confluent, even to the extent of an erythroderma within which there are "islands of sparing" of normal skin, a finding not seen in KLC.

Lupus erythematosus: Lupus erythematosus and KLC may present themselves as red macules and patches, papules, and keratotic plaques on trunk, extremities, and face, but in lupus erythematosus lesions develop especially on sites exposed to rays of the sun. Lupus erythematosus, but not KLC, may present itself at times with vesicles and bullae. Scarring alopecia may be encountered in lupus erythematosus, but not in KLC.

Mycosis fungoides, especially manifestations infundibulocentric and parakeratosis variegata: Mycosis fungoides as well as KLC may present itself with patches, papules, and plaques, but in mycosis fungoides those lesions may be joined by nodules and tumors, and lesions are situated especially on thighs and buttocks. A netlike pattern also may be encountered in both diseases, i.e., mycosis fungoides and KLC, but in mycosis fungoides it is pigmentation that is netlike (Parakeratosis variegata), whereas in KLC papules assume shapes reticular by way of confluence of them. Lesions of mycosis fungoides sometimes have a predilection for the face, neck, and scalp, where they also present themselves with infundibulocentric papules (alopecia mucinosa/mycosis fungoides with epithelial mucinosis), but those papules usually are arranged on a patch; infundibulocentric papules in KLC are discrete.

Correlation clinicopathologic: A discrete papule comes into being by virtue of the lichenoid infiltrate centered around an infundibulum or an acrosyringium. An erosion is consequent to atrophy of the epidermis. A comedo-like lesion consists of a plug of ortho- and parakeratosis in an infundibulum. Keratotic papules and plaques are a result of uneven acanthosis covered by parakeratosis that houses remnants of neutrophils staggered between zones of orthokeratosis.

Lichen planus, including lichen planopilaris and atrophic lichen planus: Lichen planus may be infundibulocentric and associated with plugs of corneocytes housed in infundibula, but hyperkeratosis usually is devoid of parakeratosis and remnants of neutrophils are not encountered in the cornified layer, whereas those findings are expected in KLC. Necrotic keratocytes in the basal layer may be encountered in both conditions, i.e., lichen planus and KLC, but they are more numerous in KLC than in lichen planus.

Discoid lupus erythematosus: Although parakeratosis, at times, may be present in lesions of lupus erythematosus, never is it in the form of mounds in fashion staggered und usually it does not house remnants of neutrophils. Necrotic keratocytes in the basal layer may be encountered in both lupus erythematosus and KLC, but they are more numerous in KLC than in lupus erythematosus. Infiltrates of lupus erythematosus are accompanied by deposits of mucin in the dermis, a change not encountered in KLC.

Lichenoid drug eruption: Lichenoid drug eruption often is typified by numerous necrotic keratocytes, sometimes clusters of them, and parakeratosis also is met with commonly. Usually, however, lesions are neither infundibulocentric nor acrosyringocentric. Atrophy of the epidermis is uncommon, but is present often in KLC. The infiltrate in a lichenoid drug eruption often contains eosinophils, sometimes many of them, a finding not typical of KLC.

Mycosis fungoides: Infiltrates of mycosis fungoides may be infundibulocentric in lichenoid fashion, but clusters of necrotic keratocytes and parakeratosis that house neutrophils are not findings of mycosis fungoides.

Laboratory confirmation: None exists.

Cause and mechanism: Not known.

Options for treatment: The condition is not usually responsive to treatment of any kind. Some improvement has been observed with retinoids and with PUVA therapy, but never do lesions resolve completely.