Immunopathogenesis of Lichenoid Dermatoses: Diseases on a Spectrum

The presentation focuses on the immunopathogenesis of lichenoid dermatoses, specifically lichen planus (LP), a chronic inflammatory condition affecting skin, mucosa, nails, and hair. Lichen planus presents as pruritic papules and plaques, with various features depending on the area affected. While the exact cause remains elusive, it is characterized by band-like inflammation at the dermal-epidermal junction, predominantly involving T cells in the inflammatory infiltrate. The pathogenesis is believed to include keratinocyte injury, leading to pro-inflammatory cytokine production, particularly interferon-gamma, influencing T cell activation. Despite lichen planus affecting 1-2% of the population, there are no FDA-approved treatments, prompting the use of off-label therapies such as narrowband UVB, methotrexate, and systemic therapies including Janus kinase (JAK) inhibitors. Recent studies have shown promising responses to JAK inhibitors, indicating their potential role in targeting the underlying disease mechanisms. The discussion highlights the complexity of lichen planus and its subtypes, suggesting that a deep understanding of its immunological pathways will pave the way for more effective, targeted therapies for patients who do not respond to conventional treatments.