Pityriasis rosea – evidence for and against an infectious aetiology 1
Pityriasis rosea, first named as such in 1860, probably holds the longest record for an exanthem suspected to be associated with an infection but for which an exact cause has not been found. The distinctly programmed clinical course, the lack of recurrence for most patients, and the presence of temporal case clustering provide the strongest evidence to support an infectious aetiology. Further support comes from seasonal variation and the association with respiratory tract infections, the unfavourable social and economic background of cases, and a history in some cases of contact with patients with pityriasis rosea. The apparent therapeutic efficacy of several treatment modalities does not provide strong evidence for or against an infectious aetiology. The roles of human herpesvirus 7 and to a lesser extent human herpesvirus 6 remain controversial. There exists reasonable evidence that pityriasis rosea is not associated with cytomegalovirus, Epstein–Barr virus, parvovirus B19, picornavirus, influenza and parainfluenza viruses, Legionella spp., Mycoplasma spp. and Chlamydia spp. infections. Evidence is also unsubstantiated as yet for alternative aetiological hypotheses such as autoimmunity, atopy, and genetic predisposition.(Accepted February 17 2004)
c1 Dr A. Chuh, The Bonham Surgery, Shop B5, Ning Yeung Terrace, 78 Bonham Road, Ground Floor, Hong Kong.
1 Part of this article is based on work submitted by the first author to the University of Hong Kong for the award of the degree of Doctor of Medicine. A complementary paper focusing specifically on the aetiological role of human herpesvirus 7 in pityriasis rosea is to be published in the International Journal of Dermatology.