Abstract
Case 1: A 50 year old male with a history of resolved discoid lupus erythematosus presented for a rash on the extremities that spread to the trunk over 6 months. Examination revealed hyperpigmented, lichenoid, violaceous patches on his trunk and extremities. Clinical suspicion was for lichen planus pigmentosus (LPP) vs erythema dyschromicum perstans (EDP) vs lichen planus (LP). Biopsy showed vacuolar and lichenoid dermatitis with epidermal atrophy and abundant melanophages in the papillary dermis. A diagnosis of LPP was made. Case 2: A healthy 26 year old female presented to her PCP for skin lesions that spread from her arm and breast to her trunk over 2 years with unsuccessful anti-fungal treatment. Examination revealed hyperpigmented, violaceous patches distributed on her trunk, neck, and arms. Clinical suspicion was for EDP vs LPP. Biopsy showed a normal epidermal rete ride pattern and abundant melanophages in the papillary dermis with scattered melanophages in the reticular dermis. PAS stain was negative for fungi. A diagnosis of inactive stage EDP was made. Discussion: LPP and EDP are acquired macular hyperpigmentation disorders of unknown etiology characterized brown/purple macules on the upper extremities, trunk, face, and neck, often with overlapping clinical features. Shared histologic features include superficial dermal inflammation and pigment incontinence. Unique histologic features of LPP include epidermal atrophy and lichenoid dermatitis with marked vacuolar degeneration of dermal-epidermal junction. In contrast, EDP has focal basal vacuolization and a lower density of inflammation in active stage and minimal or no inflammation in later stages. Melanophages are limited to the papillary dermis in LPP and are often also present in the reticular dermis in EDP. These cases highlight the important role of histopathology in differentiating these two disorders for appropriate therapeutic intervention. References available upon request.
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