Acantholytic hair casts: a dermoscopic sign of pemphigus vulgaris of the scalp.

We report the dermoscopic features of pemphigus vulgaris (PV) involving the scalp of a 57-year-old African-American female. Among our findings, there were hair casts - movable tubular structures that envelop the hair shafts. We suggest that the development of those casts occurs through acantholysis within the outer root sheath, a mechanism not yet considered in the literature. This report also highlights how dermoscopy may contribute to the evaluation of disease activity, especially in those cases of PV in which scalp involvement is recalcitrant to treatment. Finally, we recommend that the presence of hair casts should herald the need of therapy adjustment for better disease control.