hair casts are discrete , shiny , freely movable tubular structures that envelop the hair shafts and may clinically be misdiagnosed as nits . in 1986 , keipert considered the existence of two types of hair casts . 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 . 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 . ( 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 ) different patterns of hair loss have been reported in pv , including anagen shedding , as observed in our patient , scarring alopecia , and tufted folliculitis . some authors suggest that the scarring would result from the combination of acantholysis and secondary bacterial infection . telogen effluvium has been described in mice ; 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 . 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 .
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 .