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 . in 2001, affecting primarily intertriginous areas in lighter-skinned individuals. Characterized by hyperpigmented macules with minimal pruritus, LPPI often involves the axillae, groin, and inframammary regions. Histopathological features include atrophic epidermis, pigmentary incontinence, and a lichenoid inflammatory infiltrate. Differential diagnosis includes ashy dermatosis and post-inflammatory hyperpigmentation. LPPI's clinical course is variable, with treatments like tacrolimus and corticosteroids yielding inconsistent results.

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.