A retrospective study of lichen planus pigmentosus with focus on palmoplantar involvement

Lichen planus pigmentosus (LPP) is a rare disease characterized by persistent and asymptomatic slate-grey pigmentation, which mostly affects patients with skin types IV-VI. The face and neck are the most commonly involved sites, followed by the trunk and extremities. LPP is believed to spare the palms, soles and nails. In this report, we describe palmoplantar involvement in 10 (4.65%, 10/215) patients with LPP, and compare its clinicodemographic features with those of classic LPP. LPP lesions on the palms and soles present as asymptomatic, well-circumscribed, hyperpigmented, brown-black patches without any history of prior lichen planus lesions. They are mostly observed in young patients with rapidly spreading active disease, who often require systemic treatment to control the disease activity. Strikingly, palmoplantar involvement is frequently associated with other atypical LPP variants. It is important to identify palmoplantar involvement in LPP, as it has a different clinical course and associations compared with classic LPP.