Title : Differentiation discoid lupus erythematosus associated-scaring alopecia from lichen planopilaris by immunostaining of CD123 marker
Abstract:
Introduction:
Scarring alopecia (cicatricial alopecia) refers to disorders that are characterized by the irreversible destruction of hair follicles and permanent alopecia. Scarring alopecia is categorized into primary and secondary. Primary scarring alopecia (cicatricial alopecia) implies disorders that directly damage hair follicles. PP and DLE are the most common causes of scarring alopecia. Clinical and histological features may overlap between lichen planopilaris- associated and discoid lupus erythematosus-associated scarring alopecia; consequently, establishing a definite diagnosis may be challenging and difficult based on clinical, dermoscopic and histological features alone. These concerns underscore the need for useful adjunct diagnostic techniques, including direct immunofluorescence and Immunohistochemistry (IHC). Plasmacytoid dendritic cells (PDCs) are antigen- presenting cells that play an important role in the innate immune response. The presence of these cells and their specific distribution pattern in the tissue may help to distinguish lupus erythematosus from other inflammatory disorders such as LPP. we aimed to perform a study to evaluate the presence and distribution pattern of PDCs by immunostaining the CD123 marker in patients with LPP and DLE, which are the most common causes of primary scarring alopecia.
Method:
Twenty-four cases of discoid lupus erythematosus and 30 cases of lichen planopilaris were examined for immunostaining of the CD123 marker. The percentage and distribution pattern of plasmacytoid dendritic cells and the presence of the plasmacytoid dendritic cells clusters were evaluated in the samples.
Results:
The mean percentage of PDCs are higher in DLE slides than LPP ones and the perifollicular and perivascular region show the highest density of PDCs in both DLE and LPP. Neither DLE nor LPP showed the intraepidermal in?ltration of PDCs. The involvement of the dermal-epidermal junction and the subcutaneous region was notable in DLE specimens which the other studies had not to evaluated. The perieccrine and intrafollicular in?ltration in a small number of the DLE cases was detected but not in any of the LPP cases. Interstitial in?ltration in many of the LPP cases and small number of the DLE cases was observed. Our study is the ?rst study of its kind to evaluate the subcutaneous region for the presence of PDCs in DLE and LPP, and these cells at the subcutaneous tissue in both DLE and LPP was detected. Also, we discovered the PDCs were mostly observed along the deep part of hair follicles at the subcutaneous tissue of the LPP specimens, while they were more scattered through the subcutis in the DLE specimens. Aggregations of 10 cells or more (large cluster) were observed in half of the discoid lupus erythematosus specimens and only 2 lichen planopilaris, with 50% sensitivity and 93% specificity for differentiating discoid lupus erythematosus from lichen planopilaris. These large clusters were often localized at the perifollicular and perivascular region.
Conclusion:
We suggest that a plasmacytoid dendritic cells cluster of 10 cells or more is highly specific for distinguishing discoid lupus erythematosus from lichen planopilaris. It also appears that CD123 immunolabeling is valuable in both active and late stages of the disease.
