Keratosis lichenoides chronica L85.8

Kaposi, 1886; Wise and Rein, 1936; Nekam, 1938

Kaposi described the disease as "lichen ruber moniliformis" in 1886. With this designation, he had largely determined its aetiopathogenesis. Kaposi was thinking of a variant of lichen ruber, whereby he used "moniliformis" to emphasize the striped, pearl-cord-like, lichenoid (reddish) papules as a special feature. 74 years later, the Budapest dermatologist Lajos Sándor Nékám, born on June 4, 1868, remembered this clinical picture. Nekam reactivated the clinical picture in 1938 with the publication "Sur la question du lichen moniliforme". The term "keratosis lichenoides chronica", which is commonly used today, was introduced much later, in 1972 by M. Margolis. Margolis associated three things with this term: keratotic hyperproliferation, the lichenoid aspect and the chronicity of the dermatosis.

Rare, eminently chronic, lichenoid skin disease of unclear aetiology characterized by hyperkeratotic, moderately to severely itchy papules, plaques and excoriations. Variant of lichen planus verrucosus?

The aetiopathogenesis of spontaneously occurring cases of keratosis lichenoides chronica (KLC) is unclear.

A variant of lichen planus(lichen planus verrucosus) is being discussed.

A coincidental occurrence with anaplastic lymphoma has been described (single case). Coincidental occurrence with keratoacanthomas has also been described in sporadic KLC (Marzano AV et al. 2005)

Infections (hepatitis, glomerulonephritis, tuberculosis) are also mentioned as triggers.

In familial keratosis lichenoides chronica (FKLC), a gain-of-function mutation (GOF) was detected in NLRP1, the gene that codes for the NLRP1 inflammasome sensor protein. The NLRP1 protein is one of the most important inflammasome sensor proteins produced in the skin. The GOF mutation responsible for familial keratosis lichenoides chronica causes excessive activation of the inflammasome, with increased secretion of various components of the inflammasome such as CASP1, ASC, IL-1b and IL-18. This inflammasome activation leads to both inflammatory symptoms and keratinization abnormalities (Zhong FL et al. 2016). Akiyama classified diseases of this type under the term "auto-inflammatory keratinization diseases" - AiKDs. Akiyama postulated a pathogenic, primarily bidirectional relationship between autoinflammation on the one hand and genetic or acquired, functional and possibly structural disruption of the surface and/or deep epithelium of the skin (Akiyama M et al. 2020). In rare cases, there may be an overlap between familial keratosis lichenoides (FKLC) and multiple self-healing palmo-plantar carcinomas (keratoacanthomas).

Usually occurring around the age of 20 or 50; but in principle always possible (two-peaked incidence maximum curve). The clinical picture is also described for children.

Men are slightly more frequently affected than women (2:1?).

Usually spread, starting from a focal point, to large parts of the integument; trunk and extensor sides of the extremities are preferred.

Generalized, hyperkeratotic, reddish-brown, itchy, lichenoid papules that confluent into linear and reticular formations, more rarely into psoriasiform plaques.

The facial involvement is reminiscent of seborrhoeic dermatitis or atypical rosacea.

Infestation of the oral mucosa ( aphthae, laryngitis) and eyes (keratoconjunctivitis, blepharitis, synechia formation) is possible.

Palmoplantar keratoses are not uncommon. Furthermore, nail changes (raised hyperkeratotic nail fold, increased curvature of the nail plate).

Acanthosis and orthohyperkeratosis, more rarely columnar parakeratosis over sunken epidermis, also follicular keratosis, vacuolar degeneration of the stratum basale, lichenoid lymphocytic infiltrate (interface dermatitis) with focal accumulations of cytoid corpuscles and plasma cells

Dyskeratosis follicularis: atypical localization; histology is diagnostic for dyskeratosis follicularis.

Lichen planus verrucosus: the clinical and histological picture can be completely comparable. In the case of familiality, the detection of the NLRP1 mutation is conclusive.

Pityriasis rubra pilaris: rather flat, psoriasiform skin changes.

Parakeratosis variegata: poikilodermatic clinical picture. The particular clinical aspect with the "striated or reticularly arranged, lichenoid and atrophic, less scaly papules and plaques does not justify an independent clinical picture.

Lupus erythematosus chronicus: immunohistology is conclusive. Localizations are light accentuated.

As a rule, complete resistance to local therapeutic agents. Temporary improvement can be achieved with topical preparations containing 5-10% urea(e.g. as a formulation: urea cream hydrophilic 5 or 10% (NRF 11.71.), ^Basodexan® ointment). Glucocorticoids lead to a temporary improvement.

Alternative: Vitamin A acid ointment/cream (e.g. Cordes VAS).

Alternative: Tacrolimus ointment.

Retinoids: Acitretin (Neotigason) initial 0.5 mg/kg bw/day, maintenance therapy according to clinic. Possibly combination of PUVA therapy and retinoids according to RePUVA therapy. A combination of acitretin and methotrexate has also proved successful in one individual case (Li AW et al. 2017).

A positive response to an Efalizumab therapy was described as an individual case.

The entity of this disease, described by Kaposi in 1895, was controversial for a long time. Most authors assumed that it was a variant of lichen planus (see clinical analogs to lichen planus verrucosus), especially as neither histological nor immunohistological differences are clearly recognizable.

However, familial forms of keratosis lichenoides chronica (LKLC) with gain-of-function mutations in NLRP1 prove the independence of the disease (Zhong FL et al. 2016).

55-year-old woman who had been suffering from diffuse, persistent, slightly itchy skin lesions for 4 years, mainly affecting the face and extremities. The differential diagnosis was pityriasis lichenoides chronica, a discoid lupus erythematosus. Topical corticosteroids, calcineurin inhibitors, phototherapy, hydroxychloroquine and methotrexate were used with little effect.

Clinically, there were numerous keratotic, reddish papules with a diameter of 2-4 mm, symmetrically distributed on the upper and lower limbs and arranged in a linear reticular pattern. On the face, there were well-demarcated erythematous papules and plaques with yellowish scales, especially in seborrheic areas. It was reported that skin lesions improved with sun exposure. An additional finding was concomitant blepharitis with painful erosion of the tarsal conjunctiva of the left eye. The laboratory tests were within the normal range. Histopathologic examination revealed focal parakeratosis and hypergranulosis, band-like lymphocytic infiltrates in the dermis and exocytosis of lymphocytes at the dermal-epidermal junction. Direct immunofluorescence showed granular deposits of immunoglobulin M (IgM) at the dermal-epidermal junction.

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