Pityriasis lichenoides et varioliformis acuta and pityriasis lichenoides chronica: comparison of lesional T-cell subsets and investigation of viral associations.

BACKGROUND: Pityriasis lichenoides (PL) exhibits a broad clinical spectrum that includes both acute and chronic forms. The precise biologic mechanisms underlying PL remain unclear.

OBJECTIVES: To evaluate the immunohistochemical characteristics of PL and to investigate lesional T-cell subsets and the possible role of viral infection in its pathogenesis.

PATIENTS AND METHODS: Samples from 10 patients with PL et varioliformis acuta (PLEVA) and 13 with PL chronica (PLC) were analyzed immunohistochemically. Epstein-Barr virus early regions were assayed by in situ hybridization and T-cell receptor-γ (TCR-γ) gene rearrangements were assayed by polymerase chain reaction (PCR). We also utilized PCR to assay for human herpesvirus-8 (HHV-8) DNA in 51 patients with PL and in 25 controls.

RESULTS: Lymphocytes expressing CD8 and T-cell intracellular antigen-1 were more abundant in patients with PLEVA than with PLC, whereas CD4+ lymphocytes and FOXP3-positive regulatory T-cells were more abundant in PLC. HHV-8 DNA was present in 11 of 51 (21.6%) PL patients and 0 of 25 controls. A clonal TCR-γ gene rearrangement was observed in only one patient with PLEVA.

CONCLUSIONS: Our data suggests that PL may represent an inflammatory condition induced by various triggering agents, such as HHV-8, rather than a lymphoproliferative disorder. PLEVA, characterized by an acute course with severe symptoms, may indicate a relative lack of regulatory T-cells in comparison with PLC.