Immunophenotyping and viral studies in pityriasis lichenoides et varioliformis acuta lesions

Background: The underlying pathogenesis of pityriasis lichenoides et varioliformis acuta (PLEVA) remains unclear, although immunologic injury and viral etiology have been suggested. Objective: To evaluate and expand the immunophenotype of PLEVA and to search for possible viral pathogens. Methods: Formalin-fixed, paraffin-embedded specimens of 20 patients with PLEVA and 9 patients with common inflammatory dermatoses (ID) were studied for immunophenotyping and for human herpesvirus (HHV) 1 and 2, cytomegalovirus (CMV), HHV-8, parvovirus B19, and Epstein–Barr virus (EBV) immunohistochemistry. The presence of HHV-6, HHV-7, and enteroviruses was assayed molecularly. Results: The numbers of CD8⁺ T cells and T-cell intracellular antigen-1 (TIA-1)⁺ cells were statistically significantly higher in PLEVA compared to the ID group. Immunohistochemistry for human HHV-1 and HHV-2, CMV and HHV-8, parvovirus B19, and in situ hybridization for EBV were all negative. There was molecular evidence for HHV-7 in only one PLEVA case (5%). Molecular studies for HHV-6 and enterovirus involvement were negative in all the PLEVA specimens. Conclusions: The predominant T-cell infiltrate in PLEVA is dominated by CD8⁺ cells, and by increased numbers of TIA1⁺ cells, which may indicate a cytotoxic T-cell damage to the epidermis. Viral presence was not detected.