Is Demodex really non-pathogenic?

Abstract

Although usually considered a non-pathogenic parasite in parasitological textbooks, Demodex folliculorum has been implicated as a causative agent for some dermatological conditions, such as rosacea-like eruptions and some types of blepharitis. Several anecdotal reports have demonstrated unequivocal tissue damage directly related to the presence of the parasite. However, this seems to be exceedingly rare, in contrast with the marked prevalence of this infestation. We have had the opportunity to observe one of such cases. A 38-year-old woman presented with rosacea-like papular lesions in her right cheek. Histopathological examination revealed granulomatous dermal inflammation with a well-preserved mite phagocytized by a multinucleated giant cell. This finding may be taken as an evidence for the pathogenicity of the parasite, inasmuch as it does not explain how such a common parasite is able to produce such a rare disease.

Demodicosis and rosacea: Epidemiology and significance in daily dermatologic practice

“…The Dd is lower in PPR than in pityriasis folliculorum. In the case of mite penetration in the dermis, [21][22][23][24][25][26][27][28][29] or simply because the immune stimulation persists, 85 granuloma with giant cells occurs inside this immune reaction (isolated inflammatory papule and granulomatous rosacea). At the lid level, the proliferation of Demodex inside the meibomian glands could be responsible for the meibomian gland dysfunction observed in rosacea and, therefore, of the secondary ocular surface impairment.…”

“…(3) erythemato telangiectasic rosacea, diagnosed on the basis of the recent consensus, 60 can reveal a pityriasis folliculorum by close examination; (4) PPR diagnosed on the basis of the recent consensus (Fig 2, B and C) 60 ; (5) granulomatous rosacea 21,23,24,26,27,29 ; (6) isolated inflammatory papule on the face (Fig 2, J) 14 and in the absence of oral contraceptive or pregnancy (Fig 2, G); (9) blepharitis, 19 conjunctivitis, or meibomite, with cylindric scales around the base of the eyelashes (Fig 2, H) 2,13,34,35 : the dermatologist confirms the ocular impairment associated with Demodex by observing some mites on 4 to 5 epilated lashes. The Demodex blepharitis 13,19,34,36 can exist with or without facial demodicosis, 19 and is a chronic disease that does not respond to usual therapies 35,36 ; and (10) follicular eczematids consisting of borderline atypical pictures, suggesting an atypical seborrheic dermatitis or an atypical rosacea, with hillocky skin, often erythematous, with orange peel aspect and/or dilated follicular orifices, 2,19 some potential papules, irregularly dispersed and not only follicular scales (Fig 2, D).…”

“…[3][4][5][6][7][8][9][10] It is usually considered as playing a pathogenic role when it multiplies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and when it penetrates the dermis. [21][22][23][24][25][26][27][28][29] To date, it has been implicated in the occurrence of a wide range of clinical features: pityriasis folliculorum, 11,13,14,[30][31][32] papulopustular rosacea (PPR), [3][4][5][6][7][12][13][14][15]17,…”

“…Isolated cases of demodicosis occurring in children [39][40][41][42][43][44][45][46] and adults [47][48][49][50][51][52][53][54][55][56][57] who are immunosuppressed have recently been reported in the literature, inducing the worldwide idea that demodicoses are rare 18,29 and occur mainly (or only) in patients with immunosuppression. 56 However, we believe that demodicoses occur frequently beyond the general population in good health, and that they both parasitically and clinically cure with acaricidal treatment.…”

Demodex spp. Positivity among Laboratory Staff, Kitchen Staff, Cleaning Workers and Nurses working in a State Hospital

“…Parazitin akne ve diğer seboreik lezyonlardan pigmentasyona neden olabileceği bildirilmiştir. Ancak bazı araştırmacılar da non-patojen olduğunu bildirmiştir (3)(4)(5)(6). Toplu yaşam yerlerinde Demodex spp.…”