Pityriasis lichenoides: a cytotoxic T-cell-mediated skin disorder. Evidence of human parvovirus B19 DNA in nine cases.

Background: Pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC) probably represent the polar ends of the same pathologic process, i.e. pityriasis lichenoides (PL), with intermediate forms in between.

Cytotoxic mycosis fungoides evolving from pityriasis lichenoides chronica in a seventeen-year-old girl. Report of a case.

Pityriasis lichenoides chronica and its acute form, pityriasis lichenoides et varioliformis acuta, are skin diseases of unknown origin, that probably represent a hypersensitivity reaction to an infective agent. Pityriasis lichenoides is often a benign disorder but, because of the presence of a clonal T cell population detected both in the chronic and acute forms, some authors have suggested that it may belong to the group of primary cutaneous T cell lymphomas. Although various studies have clearly documented no significant association between pityriasis lichenoides and malignant lymphomas, cases of long-standing pityriasis lichenoides evolving into mycosis fungoides have been described.