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Human demodex folliculorum & brevis
Demodex Folliculorum
Demodex folliculorum and Demodex brevis
• 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.
It is grouped as
Arthropoda/Chelicerata/Arachnida/Acarina/Demodicidae/Demodex/Demodex
folliculorum or Demodex brevis
Demodex folliculorum (SEM)
Demodex folliculorum (SEM)
Demodex folliculorum (SEM)
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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.
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.
Braz J Infect Dis vol.13 no.2 , 20O9
Scalp folliculitis with Demodex: innocent observer or pathogen?
Acta Derato -sifilo
94 no.2, 2OO3
Demodex folliculorum
Demodex folliculorum
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Pityrosporum folliculitis
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Perioral dermatitis
Demodex folliculorum residing in hair follicle
Demodex folliculorum
Demodex brevis
Granulomatous rosacea-like demodicidosis
Lee & Hsu
Dermatology Online Journal 13 (4): 9 , 2OO7
Domedex
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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:
@ 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)
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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.
Demodex blepharitis
Terminology of demodicosis
British Journal of Dermatology
Chen & Plewig : 170, 1219–1225, 2014
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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:
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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
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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
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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 classification
British Journal of Dermatology
Chen & Plewig : 170, 1219–1225, 2014
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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.
Human demodicosis: revisit and a proposed classification
British Journal of Dermatology
Volume 170, Issue 6, pages 1219–1225, June 2014
• 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 classification
British Journal of Dermatology
Volume 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 46year-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 classification
British Journal of Dermatology
Volume 170, Issue 6, pages 1219–1225, June 2014
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Nodulocystic demodicosis.
Primary human demodicosis with intense
inflammatory reaction including pus and suppurative
succulent changes.
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Papulopustular demodicosis.
Primary human demodicosis displaying
disseminate involvement of the face of a 64-yearold woman with mild keratotic inflammatory papules
of different sizes in an asymmetric distribution.
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peri-oral dermatitis and blepheritis
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Crusted demodicosis of the face.
Primary human demodicosis showing multiple partly
confluent papulopustules with thick yellowish crust
Rather & Hassan , Indian J Dermatol. 2012 : 57, 72–73.
Facial Demodicidosis
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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 blepharoconjuctivitis , grover's disease, eosinophilic
folliculitis, papulovesicular facial, papulopustular
scalp eruptions, pityriasis folliculorum, pustular
folliculitis, Demodex abscess, and demodicosis
gravis (granulomatous rosacea like demodicosis).
Rosacea (a) and steroid induced rosacea (b)
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Dissecting folliculitis leading to cicatricial alopecia
Non specific
dermatitis
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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.
Ind. J. Derm Volume 59(1); Jan-Feb 2014
demodex mites on dogs
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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-tohuman 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
Demodex in Cats
Unusual feline ailment