To determine the extent of clonal outgrowth in the lymphocytic tissue infiltrate of lichen sclerosus (LS). The presence of T cells with a monoclonally rearranged T-cell receptor γ-gene (TCRγ) has been described in up to 50% of biopsies of vulvar and penile LS.Material and results
We analysed 33 foreskin specimens with LS for the presence of clonal T cells by conventional polymerase chain reaction (PCR) analysis and with TCRγ-PCR-based fluorescent fragment analysis. Eighteen of 33 patients revealed a band indicating a monoclonally rearranged TCRγ on conventional PCR analysis. Subsequent TCRγ-PCR-based fluorescent fragment analysis identified 8/18 patients with monoclonal T-cell DNA ranging from 1.4% to 23.1% of total T-cell DNA analysed and a size range from 56 to 72 base pairs. Four of 18 patients had an oligoclonal and 6/18 patients revealed a polyclonal banding pattern. The lymphocytic infiltrate contained low numbers of γδ T cells and cytotoxic T cells in comparable numbers to the low percentage of clonal TCRγ DNA.Conclusions
The low percentage of clonal TCRγ DNA argues against a systemic neoplastic disease, but rather for a local immune disorder. The target antigen of the clonal outgrowth is unknown, but an exaggerated antigen-dependent proliferation of T cells due to chronic local antigen exposure, probably an infectious antigen, is the most likely explanation.