Detection of expanded T cell clones in skin biopsy samples of patients with lichen sclerosus et atrophicus by T cell receptor-gamma polymerase chain reaction assays

Lichen sclerosus et atrophicus is a chronic dermatosis of unknown etiology and pathogenesis. Lichen sclerosus et atrophicus associated skin lesions sh ow T cell enriched infiltrates, sometimes resembling the histologic picture of early mycosis fungoides. It is supposed that the infiltrating T cells p articipate in the pathogenesis of atrophy and sclerosis. We investigated sk in biopsies from 39 lichen sclerosus et atrophicus patients by histology, i mmunohistochemistry and, in order to establish the status of T cell clonali ty, by polymerase chain reaction amplifying the T cell receptor-gamma rearr angements. A stage-dependent shift of the CD3-positive T cells was observed from a predominantly CD4-positive to a predominantly CD8-positive phenotyp e. The increase of CD8-positive cells was associated with more pronounced e pidermotropism and basal degeneration. Nearly all CD8-positive cells expres sed cytotoxic granules (TIA1), possibly causing the basal destruction. In t he late fibrotic stage of the disease, only a weak or no infiltrate was fou nd. Regarding the T cell receptor-gamma polymerase chain reaction, the pres ence of clonally expanded T cells was demonstrated in 19 of 39 patients (49 %) by at least one of two different high resolution electrophoresis techniq ues applied to separate the amplification products. Thus, for the first tim e clonally expanded infiltrating T cells were detected in lichen sclerosus et atrophicus. Furthermore, this is one of the first reports on the detecti on of clonally expanded infiltrating T cells in an inflammatory skin diseas e. The clonal T cells could not be assigned to the CD4 or CD8 subtype. Most likely, their presence is not the result of a malignant transformation but a response to an as yet unknown lichen sclerosus et atrophicus associated antigen.