Postoperative pressure-induced alopecia: report of a case and discussion of the role of apoptosis in non-scarring alopecia.

We report a case of postoperative pressure induced alopecia in a 21-year-old black female after multiple intraoperative procedures. The histopathology is distinctive and demonstrated features in common with trichotillomania and alopecia areata, including the presence of pigment casts, catagen follicles, melanophages and apoptotic bodies. External hair manipulation is considered the primary event in the etiology of pigment casts, however, our present case demonstrated numerous pigment casts despite a complete lack of evidence of external hair manipulation. We performed pattern analysis and in situ end-labeling in 19 cases of non-scarring alopecia. Pigment casts were seen in postoperative alopecia (1 case), alopecia areata (1 case) and trichotillomania (5 cases). These forms of alopecia have in common the sudden termination of the anagen phase of the hair cycle. When the anagen portion of the hair cycle is prematurely disrupted hairs enter into catagen. Pigment casts may represent a non-specific reaction pattern of follicles that are suddenly transformed from anagen to catagen. We therefore propose that hair manipulation is not uniquely responsible for the formation of pigment casts. The primary pathophysiology resulting in the formation of pigment casts more correctly reflects the sudden termination of the anagen phase of the hair cycle.