The transformation of pityriasis lichenoides chronica into parakeratosis variegata in an 11-year-old girl.

Parakeratosis variegata is a rare disorder with unknown aetiology. In a few cases it arises from benign skin diseases such as pityriasis lichenoides et varioliformis acuta (Mucha Habermann disease) or pityriasis lichenoides chronica. However, transformation into malignant diseases such as cutaneous T-cell lymphoma has been observed. We report an 11-year-old girl with a 10-year history of pityriasis lichenoides chronica now presenting with parakeratosis variegata. Analysis of skin infiltrating T cells showed clonally rearranged T-cell receptor gamma chains occurring with a frequency of more than 2%. This finding is compatible with the clinical observation of parakeratosis variegata transforming into a malignant T-cell disorder. We therefore suggest that patients suffering from parakeratosis variegata and other diseases such as pityriasis lichenoides et varioliformis acuta or pityriasis lichenoides chronica should be continuously monitored.