Pityriasis rosea during omalizumab treatment for chronic spontaneous urticaria

Pityriasis rosea (PR) is an exanthematous disease whose etiology is related to reactivation of herpes human herpesviruses 6 (HHV-6) and 7 (HHV-7). We observed two cases of PR arising during omalizumab therapy for chronic spontaneous urticaria (CSU). Here we report for the first time PR occurring during omalizumab treatment. After PR diagnosis, viral serology was performed. Data in literature about omalizumab mechanism of action, PR and HHV-6/7 infection were analyzed in order to identify possible correlations. In both our cases IgM against HHV-6 and HHV-7 were negative. The first patient presented altered IgG titers for both viruses (1:160 and 1:80, respectively) while only HHV-6 IgG (1:320) were detected in the second patient. From data in literature, we consider it presumable that apoptotic immune cells due to omalizumab immunomodulation could release viral proteins produced from integrated DNA. This could elicit cutaneous cross-reactivity and PR onset. In conclusion, we think there is a link between omalizumab therapy and PR occurring in patients with CSU. Our case history is too small to draw firm conclusions. Data collection of similar cases could be helpful to improve our knowledge.