Plasmacytoid Dendritic Cell Marker (CD123) Expression in Scarring and Non-scarring Alopecia

Classification of scarring alopecia poses a major problem, as there is considerable clinicopathologic overlap, particularly between lupus erythematosus (LE) and lichen planopilaris (LPP), especially in later stages. CD123 positive plasmacytoid dendritic cells (PDC) have been shown recently to be present in all forms of LE and are touted to be useful in differentiating LE from other scarring alopecias. Their distribution in non-scarring alopecia is not well documented. This is the first study that examines the PDC in both scarring and non-scarring alopecias. OBJECTIVE: To study the expression patterns of PDC in cases of both scarring and non-scarring alopecia. MATERIALS AND METHODS: A total of 69 cases of alopecia (48 scarring, 21 non-scarring) were studied for CD123 expression by immunohistochemistry. RESULTS: Among the scarring alopecias, 17/20 LE cases showed PDC in contrast to 1/22 LPP cases. This difference was statistically significant (P = 0.0001). 1/2 cases of folliculitis decalvans showed PDC. None of the cases of unclassified scarring alopecia were positive. In the non-scarring group, 19/20 cases of alopecia areata and a single case of trichotillomania lacked PDC. CONCLUSION: The finding of CD123 expressing PDC appears to be a promising parameter in distinguishing LE from other forms of alopecia.