Demodex folliculitis B88.0

Ayres 1930

Rare chronic clinical picture with grouped, follicularly bound papules in saprophytic colonization of the sebaceous follicles with the approximately 0.03 cm large Demodex folliculorum and other Demodex species (e.g. Demodex brevis). Humans are the exclusive host for these parasites. However, the clinical picture is also known in veterinary medicine (e.g. in certain breeds of dogs). The occurrence of porcine demodicosis (Demodex phylloides) has been reported in Brazil (Bersano JG et al. 2016).

Older adulthood (50-70 years)

Also in younger HIV-infected persons (30-40 years)

Occasionally also in immunocompetent adolescents and young adults

Especially face, cheeks, eyelids, eyelid margins.

Chronic, usually unilateral, red, chronic plaques persisting for months with mostly disseminated, 0.1-0.2cm, follicular, red or red-brown nodules and pustules; often scaling and crusting. If prolonged, reddening of the affected areas. Rarer are furunculoid nodules, so that the clnic picture may resemble acne conglobata (Demodex folliculits conglobata). Pityriasiform scaling of the affected areas.

Occasional accompanying pruritus.

In case of infestation of the eyelids(Demodex blepharitis, infestation of the meibomian glands): crusting of the eyelid margins and eyelid margin eczema, photophobia and foreign body sensation.

To what extent the frequent occurrence of the Demodex mite plays a role in the pathogenesis or exacerbation of rosacea is still unclear.

Demodex folliculitis in childhood is observed in acute lymphocytic leukemia.

3-5 or even more mites in a dilated follicle; perifollicularly arranged, inflammatory, partially epitheloid-cell infiltrate, spongiotic follicular epithelium; possibly perifollicular, granulomatous inflammation with rupture of the follicular epithelium.

Histology and clinic. Mites are very conspicuously detectable in the follicles in all stains!

For direct mite detection, a special horny layer tear-off with a cyanoacrylate fast adhesive is suitable. This is placed on a glass slide and immediately pressed onto the cheek skin. After a short time (60 seconds), the slide can be carefully unrolled. This pulls the follicle filaments with the mites out of the sebaceous gland openings. They can be assessed microscopically (Melnik B 2018).

An alternative would be confocal laser microscopy examination.

20 MHz sonography is also a suitable method to visualize follicular structures.

Rosacea

Bacterial folliculitis

perioral dermatitis

facial tinea

Remember! In case of unilateral skin changes and if the response to "classic rosacea therapy" is poor, think of demodicosis!

Therapy with 10% crotamiton emulsions (e.g. Eraxil Lotio). Treatment on 2 consecutive days, then 1 week therapy break, renewed treatment cycle.

Alternatively permethrin cream, benzyl benzoate (e.g. Antiscabiosum 10% emulsion), allethrin (e.g. Jacutin N spray) or ivermectin (1.0-2.0%) in a cream base (available as finished drug "Soolantra®").

Otherwise 1-2% metronidazole creams e.g. as a formulation - hydrophilic metronidazole cream, or gels (as finished drug e.g. Metrogel® or as a formulation - 2% hydrophilic metronidazole gel ) s.a. rosacea.

• Mites can be partially mechanically expressed at the edge of the eyelid.

Notice! External glucocorticoid applications are strictly prohibited!

If local therapy is not sufficient, metronidazole (e.g. Clont 3x 250-300mg/day for 1-2 weeks - not helpful in all cases) can be used.

Alternative: therapy trial with doxycycline (e.g. Doxycycline Stada) 2 times/day 100 mg p.o.

Alternative: In the idea that retinoids can deprive the mites of their livelihood, isotretinoin (e.g. isotretinoin-ratiopharm; acne normin) should be discussed in severe cases. Dosage: Initial 0.5 mg/kg bw/day p.o., maintenance therapy 10-20 mg/day p.o.

Alternatively: Ivermectin 150-200 μg/kg KG p.o. as ED.

42 year old Latin teacher has been noticing periocular localized inflammatory nodules for over 1/2 year. Little itching. Therapy resistance despite carefully performed therapy prescribed by the general practitioner. On inquiry also some glucocorticoid-containing ointments.

Findings: Periocular, red and reddish-brown follicular nodules, densified towards the eye and extending to the periphery. In some areas, the erythema is flat and not very scaly.

Histology: Perifollicular granuloma; several follicular mites detectable.

Therapy: Treatment with 10% Crotamiton emulsion 2 times/day. After 6 weeks complete healing of the lesions.

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2. Bersano JG et al. (2016) Demodex phylloides infection in swine reared in a peri-urban family farm located on the outskirts of the Metropolitan Region of São Paulo, Brazil. Vet Parasitol 230: 67-73.
3. Cotliar J et al (2013) Demodex folliculitis mimicking acute graft-vs-host disease. JAMA Dermatol 149:1407-1409
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11. Weingartner JS et al (2012) What is your diagnosis? Demodex folliculitis. Cutis. 90:65-66
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