Superimposed linear lichen planopilaris: another polygenic disorder exemplifying a new genetic concept.

In a few cases, polygenic skin diseases show a segmental arrangement of the lesions and at the same time a milder non segmental involvement. This phenomenon has been described as superimposed segmental manifestation. Here, we report a patient who had developed itching papules on the right side of the trunk and neck together with a scarring alopecia of the scalp. Additionally, the patient showed perifollicular papules on the abdomen leading to truncal alopecia. The histopathological analyses of skin biopsies taken from the scalp and abdomen revealed a lichen planopilaris. Interestingly, the involvement of the scalp and the chest followed the lines of Blaschko, whereas the abdominal skin lesions did not show a segmental distribution, so that a superimposed lichen planopilaris could be diagnosed. This is to our knowledge the first described case of a superimposed lichen planopilaris.