Distinguishing immunohistochemical features of alopecia areata from androgenic alopecia.

BACKGROUND: Distinction between alopecia areata (AA) and androgenic alopecia (AGA) can be made according to clinical presentation and biopsy findings. However, it is sometimes difficult to differentiate them, especially when the diffuse pattern of both AA and AGA is in the differential diagnosis of hair loss in androgen-dependent areas.

OBJECTIVES: To evaluate the characteristics of inflammatory cell infiltration using CD3, CD4, CD8, and CD20 antigens, in AA and AGA to find some consistent histological clues for distinguishing these two entities.

METHODS: A retrospective analysis of patients with diagnosed AA (30 cases) and AGA (30 cases) was performed based on the clinical and histopathological criteria. We studied immunohistochemical findings for CD3, CD4, CD8, and CD20 in all selected cases.

RESULTS: Immunohistochemical stains for CD4 and CD20 were not helpful in differentiating AA from AGA, but the inflammation density for AA was significantly (P-value = .025, .001) higher than AGA in CD3 (specificity= 86.7% and sensitivity= 96.7%) and CD8 (specificity= 50% and sensitivity=86.6%). Our findings revealed that intrafollicular CD3 (P-value = .017) and CD8 (P-value = ˂.001) infiltrations were significantly higher in AA samples in comparison with AGA.

CONCLUSION: Characterization of CD3 and CD8 in IHC samples is helpful, especially when the density of CD3 and CD8 T cells are significant in more than 50% of the infiltrated cells and are located intrafolliculary. Moreover, the most specific and sensitive test for differentiating of AA from AGA is CD3.