Pityriasis rosea and herpesviruses: facts and controversies.

Pityriasis rosea is an acute exanthem with many clinical and epidemiologic features of an infectious disease. To date, human herpesvirus (HHV)-6 and HHV-7 appear to be the most indicted culprits, and the evidence in favor of this hypothesis and the controversial results produced elsewhere are discussed. The complex pathophysiology of HHV-6 and HHV-7 infection, their diffusion in the population at large, the difficulties of understanding whether the infection is still latent or is clinically manifest, and well as whether pityriasis rosea depends on a reinfection or on a viral reactivation, all make the issue extremely difficult to study and understand.