Relapsing pityriasis rosea.

To assess the prevalence of relapses of pityriasis rosea (PR), a retrospective cohort study investigated all PR cases diagnosed in Genoa between 2000 and 2013 and followed them up to today. Of 570 cases, 21 (3.7%) relapsed. Most of them had a single episode, but 4 had two episodes and 2 had three episodes. The herald patch was always absent, size and number of the lesions were reduced, and duration was shorter than that of the primary episodes. Constitutional symptoms were present, though less severe than in the primary eruption. Most recurrences occurred within 1 year (16/21, 76.2%). Men outnumbered women and the mean age of the relapsing patients (20.3 years) was higher than that for the primary episode. A pathogenetic hypothesis is provided: since PR is associated with reactivation of human herpesvirus 6/7, a parallelism with other typical reactivating human herpesviruses (varicella zoster virus and Epstein-Barr virus) has been established.