yes its a horrible disease...



Pathophysiology: PR has often been considered to be a viral exanthem. Its clinical presentation supports this concept. PR has been linked to upper respiratory infections, it can cluster within families and close contacts, and it has an increased incidence in individuals who are immunocompromised. As with viral exanthems, the incidence may increase in the fall and the spring. A single outbreak tends to elicit lifelong immunity.
Immunologic data suggest a viral etiology. Increased amounts of CD4 T cells and Langhans cells are present in the dermis; this observation may indicate viral antigen processing and presentation. Also, anti-immunoglobulin M (IgM) to keratinocytes has been found in patients with PR; this finding may be associated with the exanthem phase of the presumed viral infection.
Despite these tendencies, no single virus has been proven to cause the disease. A number of viruses have been studied for a link to PR. Picornaviruslike particles have been seen in the tissue of African green monkeys inoculated from human PR lesions. A follow-up study failed to find picornavirus RNA in patients with PR. A recent study showed no increase in anti-IgM to parvovirus B19, making this etiology less likely. Serology and polymerase chain reaction for viral DNA has been negative for Epstein-Barr virus, parvovirus B19, and cytomegalovirus in patients diagnosed with PR.

http://www.emedicine.com/derm/topic3335.htm