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Human demodex folliculorum & brevis. Demodex Folliculorum.
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D. folliculorum is more commonly localized to the face, while D. brevis is more commonly found on the neck and chest. D. folliculorum is usually found in the upper canal of the pilo-sebaceous unit at a density of ≤ 5/sq cm and uses skin cells and sebum for nourishment. D. brevis, on the other hand, burrows deeper into the sebaceous glands and ducts and feeds on gland cells. Some authors consider the density of > 5 mites per follicle as a pathogenic criterion. Demodex folliculorum and Demodex brevis
It is grouped as Arthropoda/Chelicerata/Arachnida/Acarina/Demodicidae/Demodex/Demodex folliculorum or Demodex brevis
D. folliculorum is more commonly localized to the face, while D. brevis is more commonly found on the neck and chest. Infestation with D. folliculorum is more common than with D. brevis, but the later has wider distribution on the body. D. folliculorum is usually found in the upper canal of the pilo-sebaceous unit at a density of ≤ 5/sq cm and uses skin cells and sebum for nourishment. Several mites, with heads directed toward the fundus, usually occupy a single follicle. D. brevis, on the other hand, burrows deeper into the sebaceous glands and ducts and feeds on gland cells. Penetration of Demodex into the dermis or, more commonly, an increase in the number of mites in the pilo-sebaceous unit of > 5/sq cm, is believed to cause infestation, which triggers inflammation.Some authors consider the density of > 5 mites per follicle as a pathogenic criterion. Demodex folliculorum (SEM)
Braz J Infect Dis vol.13 no.2 , 20O9Scalp folliculitis with Demodex: innocent observer or pathogen?
Demodex folliculorum Pityrosporum folliculitis Demodex folliculorum residing in hair follicle • Perioral dermatitis
Granulomatous rosacea-like demodicidosis Lee & Hsu Dermatology Online Journal 13 (4): 9 , 2OO7
It has not yet been established if demodex is responsible for any skin diseases but increased numbers of demodex mites have been observed in the following conditions: Around 65 species of domedex are known. The historical classification of Demodex mites has been based on their hosts and morphological features. Genome sequencing has proved to be a very effective taxonomic tool in phylogenetic studies and has been applied in the classification of Demodex. Mitochondrial 16S rDNA has been demonstrated to be an especially useful marker to establish phylogenetic relationships. Domedex @ Pityriasis folliculorum’ – rough, dry and scaly skin @ Rosacea, particularly asymmetrical papulopustular or granulomatous variants @ Some cases of perioral dermatitis @ Blepharitis (inflammation of the eyelid margins)
Terminology of demodicosisBritish Journal of DermatologyChen & Plewig : 170, 1219–1225, 2014 • The human domedicosis are classified into: • A. Two species: Domedix folliculorum & domedix brevis • B. Two clinical variants: The primary form & the secondary form • The present terminology describing human demodicosis is confusing. It may include pityriasis folliculorum, rosacea-like (rosaceiform) dermatitis, demodectic rosacea, Demodex facial dermatitis, granulomatous rosacea-like dermatitis, perioral/periorbital dermatitis-like demodicosis, facial demodicosis, pityriasis folliculitis, scalp folliculitis, favus-like scalp demodicidosis, Demodex abscess and facial abscess-like conglomerates. • Chen & Plewig (2O14) proposed the following classification to describe primary demodicosis into the following three clinical forms:
1. Spinulate demodicosis: currently known as pityriasis folliculorum • Discrete fine, whitish, partly yellowish, spiky, changes involving sebaceous hair follicles, with or without faint erythema and little inflammation1. Spinulate demodicosis: currently known as pityriasis folliculorum • Discrete fine, whitish, partly yellowish, spiky, changes involving sebaceous hair follicles, with or without faint erythema and little inflammation • 2. Papulopustular demodicosis, perioral demodicosis, periorbital demodicosis, periauricular demodicosis • Papulopustules involving mostly the face, in patients without (primary form) or with pre-existing inflammatory dermatoses such as rosacea or perioral dermatitis (secondary form). The inflammatory stages show predilection for perioral, periorbital and periauricular regions • 3. Nodulocystic/conglobate demodicosis • Intense immune reaction with massive follicular and perifollicular inflammatory infiltrates caused by Demodex proliferation, pus accumulation and suppurative succulent changes The primary human demodicosis is clinically characterized by (i) late onset, usually after age 40 years and especially in the elderly population (ii) facial involvement, typically affecting periorificial areas (perioral, periorbital or periauricular) (iii) usually asymmetric distribution, grouped in an irregular shape with satellite lesions within one affected area; (iv) being follicle bound (v) being asymptomatic or mildly pruritic. The affected patients usually lack classical manifestations of rosacea, such as erythema, transient flushing or telangiectasias.
Human demodicosis: revisit and a proposed classificationBritish Journal of DermatologyChen & Plewig : 170, 1219–1225, 2014 • Examples of skin diseases or situations associated with secondary demodicosis (Chen & Plewig, 2O14) • @ Inflammatory dermatoses • Perioral dermatitis, Papulopustular rosacea ,Seborrhoeic dermatitis , Steroid dermatitis • @ Treatment-associated diseases • Epidermal growth factor receptor inhibitors ,Phototherapy, • @ Tumours • Melanocytic naevi , Eyelid basal cell carcinoma , Mycosis fungoides • @ Systemic diseases • Chronic renal failure • Secondary domedicosis can occur early in life & show amore diffuse facial distribution or trunk involvment with more extensive inflammation. Past history of underlying diseases such as perioral dermatitis or rosacea are usually observed.
Spinulate demodicosis. Primary human demodicosis depicting discrete, fine, whitish, partly yellowish, keratotic, spiky scaly changes involving sebaceous hair follicles in the background of faint erythema. Human demodicosis: revisit and a proposed classificationBritish Journal of DermatologyVolume 170, Issue 6, pages 1219–1225, June 2014
Papulopustular demodicosis. (a) Primary human demodicosis characterized by a typical protracting course involving the forehead of a 46-year-old man with agminated follicle-bound lesions in an irregular shape. (b) Microscopic examination of skin scrapings revealed more than 5 mites per cm2. Human demodicosis: revisit and a proposed classificationBritish Journal of DermatologyVolume 170, Issue 6, pages 1219–1225, June 2014
Human demodicosis: revisit and a proposed classificationBritish Journal of DermatologyVolume 170, Issue 6, pages 1219–1225, June 2014 Nodulocystic demodicosis. Primary human demodicosis with intense inflammatory reaction including pus and suppurative succulent changes. Papulopustular demodicosis. Primary human demodicosis displaying disseminate involvement of the face of a 64-year-old woman with mild keratotic inflammatory papules of different sizes in an asymmetric distribution.
peri-oral dermatitis and blepheritis Crusted demodicosis of the face. Primary human demodicosis showing multiple partly confluent papulopustules with thick yellowish crust
Clinical manifestations: ( Rather & Hassan 2O14) @ Domedex rosacea @ Non specific facial dermatitis @ Steroid rosacea The role of D. folliculorum in the pathogenesis of topical corticosteroid-induced rosacea is controversial. It has been reported that the population of Demodex mites is increased in these patients. @ Androgenetic alopecia Demodex has been implicated in the etiology of AGA @ Madarosis @ Lupus miliaris disseminatus faciei @ Dissecting folliculitis @ Miscellaneous conditions Increased number of Demodex mites has also been observed in peri-oral dermatitis , acarica blepharo-conjuctivitis , grover's disease, eosinophilic folliculitis, papulovesicular facial, papulopustular scalp eruptions, pityriasis folliculorum, pustular folliculitis, Demodex abscess, and demodicosis gravis (granulomatous rosacea like demodicosis). Rather & Hassan , Indian J Dermatol. 2012 : 57, 72–73. Facial Demodicidosis
Dissecting folliculitis leading to cicatricial alopecia Rosacea (a) and steroid induced rosacea (b)
Methods of detection of demodex Demodex is not easily detected in histological preparations; therefore, skin surface biopsy (SSB) technique with cyanoacrylic adhesion is a commonly used method to measure the density of Demodex It allows the collection of the superficial part of the horny layer and the contents of the pilo-sebaceous follicle; however. Other sampling methods used in assessing the presence of Demodex by microscopy include adhesive bands, skin scrapings, skin impressions, expressed follicular contents, comedone extraction, hair epilation, and punch biopsies. The resulting number of mites measured varies greatly depending on the method used. The mere presence of Demodex does not indicate pathogenesis. Rather, more important in diagnosing Demodex pathology is the density of mites or their extra-follicular location. Non specific dermatitis
Demodex canis is a ubiquitous mite. It lives on virtually every dog on earth. The mite causes symptoms in individuals whose immune systems are not able to suppress it. This occurs most frequently in juveniles with immature immune systems -- hence the symptoms are most common in puppies. Demodex canis can theoretically infest humans. However, dog-to-human transmission appears to be very rare. And, humans almost never develop symptoms from infestation with the mite. Be aware that we have our own species of Demodex -- folliculorum and brevis. These are much more common causes of symptoms in humans, and they are not spread by dogs. demodex mites on dogs
