By Gary M. White, MD
Lichen planus pigmentosus (LPP) is a variant of lichen planus in which lesions occur in the sun-exposed and intertriginous areas. The term lichen planus pigmentosus-inversus has been proposed to include this variants predilection for the body folds.
Hyperpigmented, dark brown macules on the sun-exposed areas such as the face, neck or flexural folds are typical. When flexural involvement does occur, axillary involvement is the most common, followed by the inframammary folds and groin. LPP is most common in middle-aged individuals with darker skin.
Ashy Dermatosis (ASD) is most similar clinically. LPP occurs more in sun-exposed areas than in ASD. In ASD, the melanin deposition occurs in the deeper dermis, thus producing blue-gray colored lesions from the Tyndall effect. Melanin deposits in LLP are located in the superficial dermis. Pigmented contact dermatitis appears similarly as well.
Sun avoidance and sunscreen should be recommended in cases where the pigmentation is sun-related, e.g., of the head and neck. Initial therapy should be directed at controlling the inflammation, thus allowing the pigmentation to fade. Any therapy that ignores the inflammatory component (e.g., laser alone, hydroquinone alone) is destined to fail. Since the darker skin and pigmentation can obscure the true amount of inflammation present, periodic biopsies can aid in assessing response to treatment. Sunscreen, oral hydroxychloroquine, and topical tacrolimus may be given for 2-3 months. If they fail to suppress the inflammation, cyclosporin may be considered. Once the inflammation has been suppressed, topical hydroquinone and/or laser therapy may be considered [Dermatol Ther. 2014 May 2].
Good pictures of LPP involving the axilla and the post auricular sulcus. Dermatology Online Journal 19(6)
Good pictures here of the axilla as well. Lichen planus pigmentosus inversus An Bras Dermatol. 2013 Nov-Dec; 88(6 Suppl 1): 146–149.
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