Lichen Planus Pigmentosus: An Important Differential

Overview / Definition Lichen Planus Pigmentosus (LPP) is a variant of lichen planus that predominantly presents as asymptomatic hyperpigmented macules and patches on the skin. This condition is most common in individuals with skin of color and is often seen on sun-exposed areas, such as the face, neck, and extremities. LPP is distinct from other forms of lichen planus due to its predominantly pigmentary changes without the typical inflammatory lesions. Epidemiology LPP is most frequently observed in individuals with darker skin types, particularly those of African, Asian, and Hispanic descent. The prevalence of LPP varies across different populations: More common in adults, especially those aged 30-60 years. Higher incidence in women compared to men. May be associated with underlying systemic diseases, including hepatitis C infection. Pathophysiology / Mechanism The exact etiology of LPP remains unclear, but it is believed to involve a combination of genetic predisposition and environmental triggers. Potential mechanisms include: Immune-mediated damage: Similar to classic lichen planus, LPP may be related to a T-cell mediated autoimmune response. Melanocyte alteration: Damage to melanocytes can lead to increased melanin production and subsequent skin pigmentation. Post-inflammatory hyperpigmentation: Previous inflammatory skin conditions may predispose individuals to the development of LPP. Clinical Presentation The clinical features of LPP are characterized by: Asymptomatic hyperpigmented lesions: These typically appear as brown to black macules or patches, often with irregular borders. Distribution: Commonly found on the face, neck, and upper limbs, sparing mucosal surfaces. Variability: Lesions may vary in size and can coalesce to form larger areas of pigmentation. Diagnosis / Workup Diagnosis of LPP is predominantly clinical, supported by the following: Clinical history: Evaluate for any preceding inflammatory skin conditions or medications that may have trigger