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. Herein we report the case of a girl suffering from pityriasis lichenoides since the age of 11 years, subsequently developing a CD45RO+, CD8+, TIA-1+ mycosis fungoides.