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August 2002

T-Cell Clonality in Pityriasis Lichenoides: Evidence for a Premalignant or Reactive Immune Disorder?

Author Affiliations

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Arch Dermatol. 2002;138(8):1089-1090. doi:10.1001/archderm.138.8.1089

IN THIS issue of the ARCHIVES, Weinberg and coworkers1 report studies of T-cell clonality in pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC). They confirm earlier reports that PLEVA is often a clonal T-cell disorder2,3 and that some cases of PLC are clonal as well.4 The authors found a significantly higher frequency of clonal T cells in PLEVA than in PLC and conclude that PLEVA is a benign clonal T-cell disorder arising from a subset of T cells in lesions of PLC. They speculate that a small clonal population of CD8+ T cells, usually below the level of detection by polymerase chain reaction amplification, is present in PLC and that a greater influx of CD8+ cells results in the detection of clonal T cells and clinical manifestations of PLEVA. Unfortunately, the authors were not able provide direct evidence that lesions of PLEVA are clonally derived from PLC; there were no examples of patients in whom the PLEVA clone was directly traced to prior PLC lesions. To further test the authors' hypothesis, it will be necessary to compare the clonality of T cells from multiple specimens fulfilling the criteria of PLC and PLEVA of individual patients.

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