Lichen planus

Like psoriasis, the lesions are well defined and raised. They also occur in areas of trauma—the Koebner's phenomenon. There is no constant relation to stress.

Unlike psoriasis, there is no family history. Itching is common. The distribution is on the flexor aspects of the limbs, particularly the ankles and wrists, rather than on the extensor surfaces, as in psoriasis. It also occurs on the trunk. However, localised forms of lichen planus can occur on the shin, palm, and soles or elsewhere.

Nail involvement is less common than in psoriasis. There may be thinning and atrophy of part or all of a nail and these often take the form of a longitudinal groove, sometimes with destruction of the nail plate. The oral mucosa is commonly affected with a white, net-like appearance and sometimes ulceration.

The typical flat topped lesions have a shiny hyperkeratotic lichenified surface with a violaceous colour, interrupted by milky white streaks—Wickham's striae.

Less commonly, very thick hypertrophic lesions occur and also follicular lesions. Lichen planus is one cause of localised alopecia on the scalp as a result of hair follicle destruction.

Lichen planus usually resolves over many months to leave residual brown or grey macules. In the oral mucosa and areas subject to trauma ulceration can occur.

Lichen planus (left). Lichen planus—oral mucosa (right)

Characteristics of lichen planus

Clinical features of psoriasis

Clinical features of eczema

Possible family history

Possible family history

Sometimes related to stress

Sometimes worse with stress

Itching—rare

Usually itching

Extensor surfaces and trunk

Flexor surfaces and face

Well defined, raised lesions

Poorly demarcated lesions

Hyperkeratosis

Oedema, vesicles, lichenification

Scaling, bleeding points

Secondary infection sometimes

beneath scales

present

Koebner's phenomenon

Nails affected

Scalp affected

Mucous membranes

not affected

Lichen planus—nails

Treatment

There is usually a gradual response to topical steroids, but in very extensive and inflamed lesions systemic steroids may be needed. Localised hypertrophic lesions can be treated with intralesional injections.

Similar rashes

Lichenified eczema

This is also itchy and may occur on the ankles and wrists. The edge of the lesion is less well defined and is irregular. The flat topped, shiny papules are absent.

Lichenified eczema

GJuttate psoriasis

Guttate psoriasis is not as itchy as lichen planus. Scaling erythematous lesions do not have the lichenified surface of lichen planus.

Pityriasis lichenoides

The lesions have a mica-like scale overlying an erythematous papule.

Drug eruptions

Rashes with many features of lichen planus can occur in patients taking:

• Chloroquine 1

• Chlorpropamide > The three "C"s

• Chlorothiazide J

• Anti-inflammatory drugs

• Gold preparations

It also occurs in those handling colour developers. Treatment

The main symptom of itching is relieved to some extent by moderately potent steroid ointments. Very hypertrophic lesions may respond to strong steroid preparations under polythene occlusion. Careful intralesional injections may be effective in persistent lesions. In very extensive, severe lichen planus systemic steroids may be indicated.

Guttate psoriasis—section through lesion (left); lichenified eczema—section through lesion (right)
Guttate psoriasis

Lichen planus

• Flexor surfaces

• Mucous membranes affected

• Itching common

• Violaceous colour

• Wickham's striae

• Small discrete lesions

• Lichenified

Pathology of lichen planus

As expected from the clinical appearance, there is hypertrophy and thickening of the epidermis with increased keratin. The white streaks seen clinically occur where there is pronounced thickness of the granular layer and underlying infiltrate. Degenerating basal cells may form "colloid bodies". The basal layer is being eaten away by an aggressive band of lymphocytes, the remaining papillae having a "saw toothed" appearance.

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