Conflicts of interest None.
Papulopustular rosacea, skin immunity and Demodex: pityriasis folliculorum as a missing link
Version of Record online: 24 OCT 2011
© 2011 The Author. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology
Journal of the European Academy of Dermatology and Venereology
Volume 26, Issue 1, pages 19–28, January 2012
How to Cite
Forton, F.M.N. (2012), Papulopustular rosacea, skin immunity and Demodex: pityriasis folliculorum as a missing link. Journal of the European Academy of Dermatology and Venereology, 26: 19–28. doi: 10.1111/j.1468-3083.2011.04310.x
Funding sources None. Contents of the manuscript have not been previously published and are not currently submitted elsewhere.
- Issue online: 15 DEC 2011
- Version of Record online: 24 OCT 2011
- Received: 6 April 2011; Accepted: 27 September 2011
Papulopustular rosacea (PPR) is a common facial skin disease, characterized by erythema, telangiectasia, papules and pustules. Its physiopathology is still being discussed, but recently several molecular features of its inflammatory process have been identified: an overproduction of Toll-Like receptors 2, of a serine protease, and of abnormal forms of cathelicidin.
The two factors which stimulate the Toll-like receptors to induce cathelicidin expression are skin infection and cutaneous barrier disruption: these two conditions are, at least theoretically, fulfilled by Demodex, which is present in high density in PPR and creates epithelial breaches by eating cells. So, the major pathogenic mechanisms of Demodex and its role in PPR are reviewed here in the context of these recent discoveries.
In this review, the inflammatory process of PPR appears to be a consequence of the proliferation of Demodex, and strongly supports the hypothesis that: (1) in the first stage a specific (innate or acquired) immune defect against Demodex allows the proliferation of the mite; (2) in the second stage, probably when some mites penetrate into the dermis, the immune system is suddenly stimulated and gives rise to an exaggerated immune response against the Demodex, resulting in the papules and the pustules of the rosacea.
In this context, it would be very interesting to study the immune molecular features of this first stage, named “pityriasis folliculorum”, where the Demodex proliferate profusely with no, or a low immune reaction from the host: this entity appears to be a missing link in the understanding of rosacea.