Delphi Consensus on the Distinct Clinical and Histopathological Features of Lichen Planopilaris and Frontal Fibrosing Alopecia: Insights From the Hair Diseases EADV Task Force.

Background: Frontal fibrosing alopecia (FFA) has been defined as a lichen planopilaris (LPP) variant, and both are characterized by lymphocytic scarring alopecia. Despite histopathological similarities, they differ clinically, suggesting potentially different pathogenetic factors. This Delphi study aimed to collect expert opinions to clarify the relationship between FFA and LPP.

Methods: The Delphi method was employed via an anonymous survey among experts in hair disorders from the Hair Diseases Task Force of the European Academy of Dermatology and Venereology (EADV), ensuring broad international representation. Two rounds of online questionnaires assessed the definition, clinical presentation, diagnosis, and management of LPP and FFA. The statements, developed based on an extensive literature review, were validated by the core expert panel. A 5-point Likert scale was utilized to quantify agreement levels, with strong consensus defined as ≥ 75% agreement or disagreement. Statements lacking strong consensus in the first round were revised and merged for inclusion in the second round.

Results: Seventeen experts from seven countries joined the Delphi consensus process. In the first round, 65 statements underwent qualitative content analysis, yielding strong consensus in 30.7% of cases. Participants provided written justifications for their assessments. In the second round, an increased consensus rate (53.7%) was reached after the expert panel statement's revision.

Conclusions: This study confirms that FFA and LPP are clinical variants within the same lichenoid spectrum. While moderate consensus supports FFA as a variant of LPP, uncertainties remain regarding its demographic distribution, the presence of vellus hairs, and blue-gray dots. The study refines diagnostic and management approaches but is limited by the absence of dermatopathologists and basic researchers.