Atypical Inverse Lichen Planus: Therapeutic Response to Calcineurin Inhibitors

Inverse lichen planus is an uncommon clinical variant of lichen planus characterised by involvement of intertriginous and flexural areas, where its morphology may differ from that of classical disease and overlap with other inflammatory, infectious, or neoplastic dermatoses. This case report describes the presentation, diagnostic evaluation and response to topical treatment of a 47-year-old woman with a four-month history of a pruritic and burning localised lesion confined to the left axillary fold. Physical examination showed a well-defined erythematous-violaceous plaque with erosive surface changes and peripheral whitish reticulation. Dermoscopy demonstrated reticulated whitish Wickham striae over an erythematous background. Histopathological examination revealed a band-like lymphoplasmacytic inflammatory infiltrate in the papillary dermis, vacuolar degeneration of the basal layer, acantholysis, and irregular hyperkeratosis without malignant atypia. The combined clinical, dermoscopic, and histopathological findings supported the diagnosis of an atypical unilateral presentation of inverse lichen planus. Because of the flexural location and the potential adverse effects associated with prolonged use of potent topical corticosteroids in intertriginous skin, treatment with topical tacrolimus 0.1% twice daily was selected. Treatment was associated with resolution of pruritus and burning and visible regression of erythema and the axillary plaque. This case illustrates the diagnostic value of clinicopathological correlation and dermoscopy in an unusual localised presentation of inverse lichen planus and supports consideration of topical tacrolimus as a steroid-sparing therapeutic option in selected flexural lesions.