Persistent lichen planus pigmentosus inversus in a 45-year-old woman: a decade-long clinical journey and therapeutic challenges in an uncommon dermatological variant.

Introduction and significance: Lichen planus pigmentosus inversus (LPPI), a rare variant primarily affecting non-sun-exposed areas in Caucasians, is resistant to standard treatments. This case highlights its clinical challenges and persistence. Case presentation: A 45-year-old woman with a decade-long history of light to dark brown macules and patches, initially in the axillary and inguinal regions, experienced progressive spread to her forearms, upper arms, and inframammary areas. Despite normal lab results and no significant family history or trauma, histopathology confirmed LPPI. Treatment with topical steroids, pimecrolimus, tretinoin, and oral prednisolone led to partial resolution, though irritation from pimecrolimus required reduced application. Clinical discussion: LPPI is a chronic inflammatory condition, first described by Pock Conclusion: This case report documents a rare instance of pigmented inverse lichen planus in a 45-year-old woman, highlighting its chronic nature, treatment resistance, and ongoing challenges in managing pigmentation.