Lichen planus is a chronic inflammatory condition affecting skin, mucous membranes, hair, and nails, characterized by distinctive purplish, itchy, flat-topped bumps or plaques.

Though its exact cause remains uncertain, lichen planus is understood as a cell-mediated immune disorder in which the body's immune system mistakenly attacks its own cells.

It can appear on various body parts, including the wrists, ankles, lower back, mouth, scalp, genitals, and nails, displaying diverse clinical manifestations.

Etiology and Immunopathogenesis

Lichen planus arises from an aberrant immune response, primarily involving T-lymphocytes targeting basal keratinocytes in the skin and mucosa.

While the underlying trigger remains elusive, contributing factors may include viral infections—most notably hepatitis C virus—stress, genetic predisposition, certain medications (such as antimalarials and diuretics), and allergic reactions to metal fillings in teeth. This autoimmune-like reaction causes inflammation, cell damage, and the characteristic skin and mucosal lesions.

Clinical Presentation and Variants

The hallmark signs on the skin are polygonal, shiny, violaceous (purple) papules and plaques, commonly clustered on flexural surfaces like wrists and forearms. These lesions may be intensely itchy. Involvement manifests as lacy white streaks (known as Wickham's striae), painful erosions, or ulcers inside the cheeks and on the tongue. Nail changes include thinning, ridging, and sometimes permanent loss.

Less common forms such as hypertrophic, bullous, annular, or inverse lichen planus show different patterns or more severe inflammation. Lesions can persist for months to years, and mucosal or large hypertrophic lesions often demonstrate chronicity.

Epidemiology and Associated Conditions

Lichen planus affects adults typically between 30 and 60 years of age, with no strong gender predilection. Its global prevalence varies, with estimates around 0.1% to 4%. Associations with other autoimmune diseases (such as vitiligo, alopecia areata, and myasthenia gravis) have been reported, as well as with hepatitis C infection—especially in endemic regions—suggesting shared immunologic pathways.

Diagnosis and Differential Diagnosis

Diagnosis primarily relies on clinical examination supported by histopathological analysis of skin or mucosal biopsies, revealing a band-like lymphocytic infiltrate at the dermoepidermal junction and basal cell degeneration. Differentiation from other dermatoses such as psoriasis, eczema, lupus erythematosus, or candidiasis is critical, utilizing clinical pattern recognition along with laboratory investigations as needed.

Management Strategies

Treatment aims to reduce inflammation, alleviate symptoms, and prevent complications. Mild cutaneous lesions may resolve spontaneously or respond to topical corticosteroids. Symptomatic care for lesions includes pain relief and maintaining hygiene. Regular monitoring is advised as chronic mucosal lichen planus carries a slight risk of malignant transformation.

Dermatologist Dr. Andreas Katsambas states, "Lichen planus exemplifies the complexities of immune dysregulation manifesting in cutaneous and mucosal tissues, necessitating thoughtful clinical evaluation and a tailored therapeutic approach."

Lichen planus remains a multifaceted condition with varied presentation and uncertain origins but clear immunologic basis. Deepening insights into its pathophysiology promise enhanced diagnostic precision and therapeutic innovation, ultimately improving outcomes for those affected by this often challenging disease.