Distinguishing diffuse alopecia areata (AA) from pattern hair loss (PHL) using CD3(+) T cells.

BACKGROUND: Distinguishing between diffuse subacute alopecia areata (AA), in which the peribulbar infiltrate is absent, and pattern hair loss is challenging, particularly in cases that lack marked follicular miniaturization and a marked catagen/telogen shift.

OBJECTIVE: We sought to distinguish diffuse AA from pattern hair loss using CD3(+) T lymphocytes.

METHODS: A total of 28 cases of subacute AA and 31 cases of pattern hair loss were selected and a 4-mm punch biopsy was performed. All the specimens were processed using the "HoVert" (horizontal and vertical) technique. In all cases, hematoxylin-eosin and immunohistochemical stains for CD3, CD4, CD8, and CD20 were performed.

RESULTS: The presence of CD3(+) lymphocytes within empty follicular fibrous tracts (stela), even without a concomitant peribulbar infiltrate, is a reliable histopathological clue in supporting a diagnosis of AA (sensitivity 0.964, specificity 1, P ≤ .001).

LIMITATIONS: Limited tissue for analysis remained in the clinical sample tissue blocks.

CONCLUSION: The presence of CD3(+) T-cells within empty follicular fibrous tracts (stela) supports a diagnosis of AA.