Lichen planus pigmentosus

Lichen planus pigmentosus (LPP) is a rare variant of lichen planus characterized by the insidious onset of dark brown to slate-gray hyperpigmented macules and patches on the skin, predominantly affecting sun-exposed areas such as the face, neck, and flexural folds. It is also sometimes referred to as lichen planus pigmentosus-inversus when it predominantly involves intertriginous (skin fold) areas. The condition primarily affects the integumentary system (skin) and is considered a pigmentary disorder within the lichen planus spectrum. It is more commonly reported in individuals with darker skin types, particularly in populations from the Indian subcontinent, the Middle East, Latin America, and other tropical regions. Clinically, LPP presents as diffuse or reticulated (net-like) hyperpigmented patches that develop gradually without a preceding inflammatory phase, which distinguishes it from classic lichen planus. The lesions are typically asymptomatic, though some patients may experience mild pruritus (itching). Unlike classic lichen planus, the characteristic Wickham striae and violaceous papules are usually absent. Histopathologically, the condition shows pigment incontinence with melanophages in the upper dermis, along with a lichenoid lymphocytic infiltrate at the dermoepidermal junction and basal layer degeneration. The exact cause of lichen planus pigmentosus remains unclear, though it is thought to involve an immune-mediated mechanism similar to other forms of lichen planus. Potential triggers include mustard oil application, certain hair dyes, hepatitis C virus infection, and other environmental factors. Treatment is often challenging and results can be variable. Therapeutic options include topical corticosteroids, topical calcineurin inhibitors (such as tacrolimus), topical retinoids, and photoprotection with broad-spectrum sunscreens. Chemical peels, laser therapy, and oral dapsone have also been used with varying degrees of success. The condition tends to follow a chronic, relapsing course, and complete resolution of pigmentation may be difficult to achieve.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Lichen planus pigmentosus