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.

INTRODUCTION

Hair casts are discrete, shiny, freely movable tubular structures that envelop the hair shafts and may clinically be misdiagnosed as nits.[12] In 1986, Keipert considered the existence of two types of hair casts.[3] The first was associated with parakeratotic disorders of the scalp, such as psoriasis. He denominated them parakeratotic hair casts, reflecting the cause and composition of those casts. The second, not associated with scalp disorders, was described in women and named as peripilar keratin casts. The formation of hair casts is also a well-known feature of persistent traction and, recently, Tosti et al. described them as a helpful dermoscopic clue for the diagnosis of traction alopecia.[2]

CASE REPORT

We have detected hair cast formation in a 57-year-old African-American female with pemphigus vulgaris (PV) involving the scalp. She was in her second flare of the disease with widespread blister formation. On scalp examination, there was a painful, pruritic, large eroded hairless plaque covered with yellow to black crusts [Figure 1a]. Dermoscopy of the immediate perilesional area revealed hair shafts imprisoned underneath crusts and also numerous hair casts [Figure 1b]. These structures were a few millimeters long, but sometimes encircled the hair shaft through a longer extension. Pull test was strongly positive and examination of the epilated hairs under dermoscopy showed pigmented roots with sheaths, corresponding to normal anagen hairs [Figure 1c]. Direct immunofluorescence of plucked hairs of patients with PV reveals IgG and C3 deposition on outer root sheath (ORS) keratinocytes.[4] This exam was not available at that time.

Figure 1

(a) Large, eroded, hairless lesion of PV on the scalp, covered with crusts; (b) Dermoscopy of the immediate perilesional area reveals hair casts encircling hair shafts (original magnification 10×); (c) Dermoscopy of a plucked hair showing a pigmented root with sheath, compatible with normal anagen hair (original magnification 10×)

DISCUSSION

Different patterns of hair loss have been reported in PV, including anagen shedding,[5] as observed in our patient, scarring alopecia,[6] and tufted folliculitis.[7] Some authors suggest that the scarring would result from the combination of acantholysis and secondary bacterial infection.[7] Telogen effluvium has been described in mice;[8] however, it is not a feature of the disease in humans.

Hair cast development in PV is possibly due to a mechanism not enclosed in Keipert's classification – acantholysis within the ORS. As the hair grows, part of the ORS keratinocytes is carried up through the follicular ostia to form a cylindrical structure enveloping the shaft: the hair cast. Like anagen shedding, hair casts in PV suggest a subclinical involvement of the hair follicle. Delmonte et al. considered the former as a Nikolsky sign of the scalp.[5] In our opinion, acantholytic hair casts should be regarded likewise.

To our knowledge, this is the first report of dermoscopic features of PV involving the scalp. This case 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. The presence of hair casts should be regarded by the dermatologist as a sign that acantholysis is still taking place, and possibly herald the need of therapy adjustment for better disease control.