Actinic lichen planus (ALP) is a form of lichen planus associated with sun exposure.

Features of actinic lichen planus:

(1) The lesions occur in sun-exposed skin of patients with dark skin.

(2) A lesion shows a reticulated white plaque with or without vesicles.

(3) Lesions on sun-exposed sites may be present with lesions elsewhere, or it may be limited to a single site such as the lower lip. The patient may or may not have a history of lichen planus.

(4) A biopsy of the lesion shows:

(4a) thinning of the epithelium with subepidermal clefting

(4b) interface vacuolar change

(4c) dermal band of lymphocytes, plasma cells and histiocytes

(4d) negative stains for micro-organisms

(4e) negative direct immunofluorescence

(5) Other causes of lichenoid lesions (drug eruptions, autoimmune blistering disease, Herpes simplex, etc) are excluded.

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