A meta-analysis of association between acne vulgaris and Demodex infestation

Abstract

Until now, etiology of acne vulgaris is still uncertain. Although clinicians usually deny the association between Demodex infestation and acne vulgaris, it has been proved in some clinical practices. To confirm the association between Demodex infestation and acne vulgaris, a meta-analysis was conducted. Predefined selection criteria were applied to search all published papers that analyzed the association between Demodex infestation and acne vulgaris (January 1950 to August 2011) in ISI Web of Knowledge, MEDLINE, and China National Knowledge Infrastructure (CNKI) databases. A meta-analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) based on fixed effects models or random effects models. We enrolled the 60 Chinese and 3 English papers in this meta-analysis, which covered Turkey and 25 different provinces/municipalities in China and 42 130 participants including students and residents, aged from 1 to 78 years. The pooled OR in random effects models is 2.80 (95% CI, 2.34-3.36). Stability is robust according to sensitivity analysis. The fail-safe number is 18 477, suggesting that at least 18 477 articles with negative conclusions would be needed to reverse the conclusion that acne vulgaris was related to Demodex infestation. So the effect of publication bias was insignificant and could be ignored. It was concluded that acne vulgaris is associated with Demodex infestation. This indicates that when regular treatments for acne vulgaris are ineffective, examination of Demodex mites and necessary acaricidal therapies should be considered.

Cloning and sequence analysis of chitin synthase gene fragments of Demodex mites

“…Up to now, 140 species or subspecies have been identified, infesting the hair follicles, sebaceous glands, meibomian glands, and internal organs of 11 orders of mammals such as human, dog, sheep, cat, pig, and (Izdebska, 2010;Mederle et al, 2010), goat demodicidosis (Smith, 1961;Xu et al, 2009), livestock demodicidosis (Chakrabarti and Pradhan, 1985), and human demodicidosis (Ayres and Anderson, 1932;Ayres and Ayres, 1961;Forton and Seys, 1993;Forton et al, 2005;Zhao et al, 2010;2011a;2011c;2012c). However, the pathogenesis of demodicidosis is still uncertain, and there are no effective prevention measures.…”

Another face of demodicosis

“…They feed on sebum, lymph, plasma and epithelial cells. There are many species, but the two that have been identified in human skin are Demodex brevis and D. folliculorum . It is thought that neonates are colonized shortly after birth and that mite prevalence increases with age, approaching 100% in the elderly population …”

“…It is likely that in the majority of people they are commensals, but under certain circumstances they may be pathogenic. An entity called Demodex folliculitis is recognized, but the literature argues their role in several dermatoses, including perioral dermatitis, blepharitis, and classic and granulomatous rosacea . For example, increased numbers of mites are seen in patients with rosacea compared with controls, and clinical response to topical antiparasitics is documented …”

“…Mites can be identified by microscopy of eyelashes or scrapings treated with potassium hydroxide, or with skin surface biopsy. Although the presence of small numbers of mites is not necessarily significant, detection of more than five mites per 1 cm is suggestive of pathogenicity …”

“…There are many species, but the two that have been identified in human skin are Demodex brevis and D. folliculorum. [1][2][3] It is thought that neonates are colonized shortly after birth 3 and that mite prevalence increases with age, approaching 100% in the elderly population. 3 The exact role of these mites in skin disease remains disputed.…”