Lichen planopilaris and long-standing
traction alopecia are both traditionally classified as
scarring alopecias. The etiology of
lichen planopilaris has not been fully elucidated, although an autoimmune mechanism is generally accepted with Langerhans cell involvement implicated in previous studies. The etiology of
traction alopecia is generally considered to be the result of mechanical force with subsequent
inflammation without an autoimmune component. Langerhans cells in pure
traction alopecia have not been previously evaluated nor have Langerhans cell concentrations been compared among the
scarring alopecias. We performed double immunostaining with CD1a and CD3 to assess the ratio of Langerhans cells to T lymphocytes in
lichen planopilaris and
traction alopecia. Sixteen biopsies were evaluated including 9 biopsies of
lichen planopilaris and 7 biopsies of
traction alopecia. The mean ratio of the concentration of Langerhans cells to T lymphocytes was 1.28 for the
lichen planopilaris group and 0.59 for the
traction alopecia group. There is a significantly higher ratio of Langerhans cells to T lymphocytes in
lichen planopilaris compared with that seen in
traction alopecia. This supports previous data recognizing an immune component in
lichen planopilaris mediated by Langerhans cells while emphasizing that most
traction alopecias are not primarily immune related. Thus, the traditional classification systems for
alopecia may need review and revision, especially when looking at etiopathogenesis. However, rare cases of
traction alopecia demonstrated ratios similar to those seen in
lichen planopilaris. These cases may represent the recently described "
traction alopecia" condition, cicatricial
marginal alopecia or changes seen in long-standing lesions, emphasizing the need for inclusion of distribution and duration within the clinical information.