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Clonality in PLEVA: Does It Exist and What Does It Mean?

In recent years, dominant clonal populations of T lymphocytes have been isolated in lesions of mycosis fungoides. Such populations are also found in lymphomatoid papulosis and small plaque parapsoriasis -- cutaneous lymphoproliferative disorders with the potential for malignant transformation. Researchers have long suggested that pityriasis lichenoides et varioliformis acuta (PLEVA) has a similar potential, yet only a few isolated cases of clonal rearrangements have been detected in cases of this condition. In this French study, the authors used sophisticated heteroduplex DNA analysis to examine 20 PLEVA patients for the presence of a dominant clone of T lymphocytes.

A clonal population was found in 65 percent of the cases examined, adding to evidence that PLEVA may be part of the still poorly defined spectrum of cutaneous lymphoproliferative disorders. None of the 13 patients in whom clonal T lymphocyte populations were discovered developed clinical evidence of lymphoma within 2.5 years of follow-up.

Comment: The results of this study further our understanding of the true nature of PLEVA and raise anew the issue of the clinical significance of the presence of a clonal population of T lymphocytes. The majority of patients demonstrated clonal T-cell proliferation. This finding suggests that PLEVA may be part of a spectrum of disorders involving lymphocytic infiltrates in the skin that includes small plaque parapsoriasis and lymphomatoid papulosis. The relation between these entities and cutaneous T-cell lymphoma remains unexplained, however. Very few, if any, patients with PLEVA progress to cutaneous lymphoma. The incidence of progression to cutaneous lymphoma in PLEVA patients is certainly far less than in patients with lymphomatoid papulosis. As the authors suggest, the host immune response to the neoplastic population of lymphocytes may be brisk enough to control and subdue this population of cells in the vast majority of afflicted patients. It is also possible, although perhaps less likely, that clonality does not necessarily imply neoplastic behavior. Further work is needed to clarify these issues.

— BR Smoller

Published in Journal Watch Dermatology January 12, 2001

Citation(s):

Dereure O et al. T-Cell clonality in pityriasis lichenoides et varioliformis acuta: A heteroduplex analysis of 20 cases. Arch Dermatol 2000 Dec 13 1483-1486.