Lichen Planus Pigmentosus: The Controversial Consensus

Area of Science:

• Dermatology
• Pathology

Background:

• Lichen planus pigmentosus (LPP) is a pigmented variant of lichen planus first described in India.
• LPP predominantly affects individuals with darker skin tones and presents with insidious onset of hyperpigmented macules and patches.

Purpose of the Study:

• To describe the clinical and histopathological features of lichen planus pigmentosus.
• To discuss the differential diagnosis and controversial identity of LPP with erythema dyschromicum perstans.
• To report associated conditions and variants of LPP.

Main Methods:

• Clinical observation and histopathological examination of affected skin.
• Review of existing literature on LPP and related conditions.

Main Results:

• LPP typically manifests on sun-exposed areas, sparing palms, soles, and nails.
• Histopathology reveals epidermal atrophy, basal cell vacuolar degeneration, and dermal pigment incontinence.
• Significant histopathological similarities exist between LPP and erythema dyschromicum perstans, though clinical and immunological differences are noted.

Conclusions:

• LPP is a distinct entity, despite histopathological similarities with erythema dyschromicum perstans.
• Associations with Hepatitis C virus, frontal fibrosing alopecia, Bazex acrokeratosis, and nephrotic syndrome have been reported.
• A rare variant, LPP inversus, affects covered areas and predominantly white-skinned individuals.