Track: Clinical Studies

Abstract:

Mechanical stress on the hair and scalp induced by hair pulling, tight braiding, or excoriation can contribute to several forms of alopecia, including traction alopecia (TA) and trichotillomania (TTM). Histologic features of TA include increased telogen/catagen hairs, fibrous streamers, and pauci-follicular units. Well-described histologic features of TTM include pigment casts, trichomalacia, fractured hair shafts, the “hamburger” sign, and distortions of the follicular anatomy. Subtle structural anomalies of the pilosebaceous unit have been detected, which may further assist in recognizing the contribution of mechanical stress in the evaluation of alopecia biopsies. We conducted a blinded, qualitative, and semi-quantitative retrospective study of horizontal scalp biopsy sections of clinically and histopathologically-confirmed TA (n=16) and TTM (n=9) cases compared to biopsies from controls (n=18), in which an impression of androgenetic alopecia without any inflammatory or cicatricial component was reported. Follicular keratinocyte cleavage, combined folliculostromal tearing, and isthmic inner root sheath collapse was observed more frequently in both TA and TTM compared to controls (p-value <0.04). Collapse of the inner root sheath of the suprabulbar zone and surface lichenification appeared unique to TTM (p-value <0.0002). Lateral follicular epithelial impingement at the isthmus/infundibulum and vectorially-warped sebaceous lobules appeared exclusive to TA (p ~0.05 to TTM; p < 0.0002 to controls). These alterations were often observed even in the absence of other previously described features of TA or TTM. The results of this semi-quantitative histopathologic analysis warrant further investigation into the potential diagnostic utility and reproducibility of these features in the diagnosis of mechanical alopecia.

Jonathan Lee

Affiliation

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Histopathologic Clues to “Mechanical” Alopecia: A Comparative, Qualitative, & Semi-Quantitative Analysis of the Pilosebaceous Unit