Lichen Nitidus

Background

Lichen nitidus is a relatively rare, chronic skin eruption that is characterized clinically by asymptomatic, flat-topped, skin-colored micropapules (see the image below).^[1] It mainly affects children and young adults.^[2]  Several clinical variants of lichen nitidus have been reported, and a number of disorders have been associated with it (see Presentation). Optimal therapy remains to be established.

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Multiple skin-colored shiny papules associated with lichen nitidus.

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Pathophysiology

The skin is the primary organ system affected. Mucous membranes and nails^[3] also might be involved. Lichen planus can clinically mimic lichen nitidus and can sometimes coexist with lichen nitidus.

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Etiology

The etiology of lichen nitidus is unknown. Immune responses and genetic factors have been suggested as possible contributors.^[4] Controversy exists regarding the relationship between lichen planus and lichen nitidus.^[5]

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Epidemiology

The frequency of lichen nitidus has not been defined, because of its uncommon occurrence. In a study from Togo that included 959 cases of lichenoid dermatosis in the period from January 1997 to December 2016, lichen nitidus accounted for only 23 of the 959 (2.4%).^[6]

Lichen nitidus may affect any age group, but it most commonly develops in childhood or early adulthood. No sex predilection exists. However, generalized variants appear to occur predominantly in females. No racial predilection is reported.

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Prognosis

Lichen nitidus is a benign disease with no associated mortality or complications. Although the disease may remain active for several years,  spontaneous resolution is usual.

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History

Lichen nitidus is usually an asymptomatic eruption; however, patients occasionally complain of pruritus. Familial cases have been described.^[7]

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Physical Examination

The primary lesions consist of multiple 1- to 3-mm, sharply demarcated, round or polygonal, flat-topped, skin-colored shiny papules that often appear in groups (see the image below).

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Multiple shiny lichens over the penis.

The Köbner phenomenon (or an isomorphic response) may be observed (see the image below). This phenomenon causes the occasional linear pattern of the lesions associated with lichen nitidus.

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Köbner phenomenon in lichen nitidus.

The most common sites of involvement are the trunk, the flexor aspects of the upper extremities, the dorsal aspects of the hands (see the image below), and the genitalia. Infrequently, the lower extremities, palms, soles, face, nails, and mucous membranes may be affected. Nail changes include pitting, ridging, splitting, and linear striations.

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Lichen nitidus.

Lichen nitidus has several clinical variants, including the following:

• Generalized^[8]
• Linear
• Actinic^[9]
• Perforating^[10]
• Keratodermic^[11]
• Vesicular^[12]
• Purpuric^[13]  or hemorrhagic^[12]

Diseases reported to be associated with lichen nitidus include the following:

• Atopic dermatitis^[14]
• Lichen planus^[15]
• Condyloma^[16]
• Amenorrhea^[17]
• Crohn disease^{[18, 19]}
• Juvenile chronic arthritis^[20]
• Down syndrome^{[21, 22, 23]}

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Procedures

Dermoscopy may aid in distinguishing lichen nitidus from similar-appearing conditions (eg, lichen spinolosus and keratosis pilaris).^{[24, 25]}

Reflectance confocal microscopy (RCM) has been found to be useful as a noninvasive means of differentiating lichen nitidus from facial papule dermatoses such as seborrheic keratosis, verruca plana, and syringoma.^[26]

A skin biopsy for histopathologic examination may be obtained to confirm the clinical diagnosis.

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Histologic Findings

The papule of lichen nitidus consists of a lymphohistiocytic inflammatory cell infiltrate that lies in close proximity to the epidermis and is associated with basal cell hydropic degeneration. The overlying epidermis is flattened and parakeratotic. At the lateral margins of the papule, the rete ridges extend downward and seem to hug the inflammatory infiltrate, which may be granulomatous.

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Approach Considerations

No therapeutic modality has been rigorously evaluated for the treatment of lichen nitidus, because of the rarity of the condition, its lack of significant symptomatology, and its characteristic disappearance within one or several years. Reported therapies, mostly from isolated case reports, have included the following:

• Topical and systemic steroids
• Topical tacrolimus^{[27, 28, 29]}
• Systemic cetirizine^[30]
• Levamisole^[30]
• Etretinate
• Acitretin^[31]
• Itraconazole^[32]
• Cyclosporine
• Topical dinitrochlorobenzene^[33]
• Psoralen plus UV-A light^[34]
• Narrowband UV-B light^{[35, 36, 37]}
• Natural sunlight therapy^[38]

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Prednisone (Deltasone, Prednisone Intensol, Rayos)

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Methylprednisolone (A-Methapred, DepoMedrol, Medrol)

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Cetirizine (Aller-Tec, Children's Zyrtec Allergy, Children's Zyrtec Hives Relief)

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Acitretin (Soriatane (DSC))

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Cyclosporine (Gengraf, Neoral, Sandimmune)

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Tacrolimus ointment (Protopic)

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