Plasma Cell-Predominant Lichen Planopilaris

Area of Science:

• Dermatology
• Pathology
• Immunohistochemistry

Background:

• Lichen planopilaris (LPP) is a scarring alopecia.
• It typically presents with a lichenoid interface infiltrate and follicular involvement.

Observation:

• A 52-year-old man with a 30-year history of scalp psoriasis was diagnosed with LPP.
• Initial biopsies showed lymphocyte-predominant LPP; subsequent biopsies revealed plasma cell-predominant LPP.
• Extensive immunohistochemical and special stains ruled out hematolymphoid, infectious, or autoimmune causes.

Findings:

• The LPP exhibited a robust superficial and deep lichenoid interface dermatitis.
• Plasma cells were the predominant inflammatory cells, an unusual finding in LPP.
• B-cell clonality studies were inconclusive for a clonal process.

Implications:

• This case expands the understanding of LPP's diverse histopathological presentations.
• It emphasizes the importance of considering plasma cell-rich LPP in differential diagnoses.
• Treatment with doxycycline and hydroxychloroquine showed symptomatic improvement, suggesting potential therapeutic avenues.