CD123 immunohistochemistry for plasmacytoid dendritic cells is useful in the diagnosis of scarring alopecia

Abstract

Background: Distinguishing types of lymphocytic scarring alopecia is often difficult because of the overlapping features. Recently, the presence of plasmacytoid dendritic cells (PDCs) in cutaneous lupus erythematosus (LE) was demonstrated and further shown to help distinguish lupus from other dermatoses.1-6 This study aims to determine if the presence and distribution of PDCs can aid in the diagnosis of scarring alopecia.

Methods: Cases of scarring alopecia due to chronic cutaneous lupus erythematosus (CCLE), lichen planopilaris (LPP) and central centrifugal cicatricial alopecia (CCCA) were examined histopathologically. A total of 45 total biopsies were evaluated and CD123 immunohistochemistry was performed on all samples. The relative percentage of PDCs, the presence of clusters and the distribution of CD123+ cells were noted.

Results: PDCs comprised a greater percentage of the infiltrate and were arranged in clusters in cases of CCLE vs. LPP or CCCA. In CCLE, the location of PDCs was perivascular, perifollicular, perieccrine and/or at the follicular junction. In LPP and CCCA, PDCs were mainly arranged as single, interstitial cells.

Conclusions: Our findings suggest that the presence and arrangement of CD123+ PDCs may assist in the diagnosis of scarring alopecia. We anticipate this will be of value in diagnosing challenging cases of highly inflammatory scarring alopecia.

Keywords: CD123; immunohistochemistry; lupus; plasmacytoid dendritic cell; scarring alopecia.