The histopathologic diagnosis of traction alopecia: An evidence-based model

Background: Traction alopecia (TA) is common, but histopathologic criteria for TA have not been objectively defined. Objective: Determine whether the pauci-follicular unit (PFU) can be used as a diagnostic criterion for TA. Compared to a normal follicular unit (NFU), the PFU is a noninflamed follicular unit with an intact sebaceous gland but fewer than 2 follicles. Methods: A retrospective review of 25 cases of TA and 25 cases of “normal scalp” was performed. Data included all follicles (by size and phase), sebaceous glands, and total follicular units. Results: Comparing data (traction vs normal), we found a significantly higher number of PFUs in cases of TA (median 6 vs 0, P <.001), which can be used as a helpful and easily recognizable diagnostic tool in diagnosing cases of TA. Limitations: Comparison to other forms of alopecia was not performed. Conclusions: The number of PFUs in an alopecia biopsy can be used to establish the diagnosis of TA.