Lichen Planopilaris in the Androgenetic Alopecia Area: A Pitfall for Hair Transplantation.

Background: Classic lichen planopilaris (LPP) is a patchy form of primary lymphocytic cicatricial alopecia localized on the vertex of the scalp. It is important, however, to be aware of other, less recognized presentations that may be missed without dermatoscopy and pathology.
Methods and Results: We report 26 patients with LPP presenting with subtle erythema and scaling colocalized in the area of patterned thinning (androgenetic alopecia, AGA). All patients had been treated for seborrheic dermatitis in the past. Dermatoscopy showed the presence of 2-4 hairs emerging as a tuft from the same ostium surrounded by erythema, peripilar casts and interfollicular scaling associated with hair miniaturization. Histopathology obtained from those areas corresponded to LPP with concomitant follicular miniaturization.
Conclusion: Subtle or focal cases of LPP may be missed for seborrheic dermatitis when overlapping with AGA. Dermatoscopy-guided biopsy from the affected scalp is the best approach to make a timely diagnosis. This is particularly important in patients with AGA evaluated to undergo hair transplantation, as active LPP is a contraindication for these patients.