DEMODEX MITE

INTRODUCTION• Gk - Demos - Fat ; Dex - Wormwood

• ‘The Mighty Mite’ aka ‘Eyelash Mite’ or ‘Face Mite’

• 65 known species, mostly commensal

• Phylum Arthropoda Family Demodicidae ; Suborder ; Prostigmata

• Demodex aries aurati brevis bovis canis caprae caballi cati cornei criceti equi folliculorum gapperi gatoi injai ovis phyloides zalophi

INTRODUCTION

• Isolated from Cerumen by Jakob Henle (1841) • Gustav Simon described as Acarus folliculorum

(1842)

• Demodex coined by Richard Owen (1843)

DEMODEX

• Obligate Pilosebaceous gland parasites – Man / Dogs / Cats (Mange)

• 02 main species :

D. Folliculorum (Longer 0.2 – 0.4 mm)D. Brevis (0.1 – 0.2 mm / Sebaceous)

• A

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PATHOGENESIS• Contain Lipase ; found in areas high with sebum viz forehead,

cheeks, nasolabial folds, scalp, external ear, in eyelash follicles meibomian glands, upper chest and nipples

• D. folliculorum - head-down position in the follicle, often with the tip of the abdomen protruding from the follicular orifice.

• Follicle mites are quite motile, and migrate from follicle to follicle. Most infested follicles contain two to six mites, but occasionally they are much more numerous.

• Mites have been isolated from individuals of all ages, except neonates (close maternal contact?)

• Prevalence inc with age

• Skin-surface biopsy / scraping identifies clusters

CLINICAL FEATURES

• 02 distinct presentations:

• 1) PITYRIASIS FOLLICULORUM

Earlier described in Middle-aged or older women who rarely washed their faces, but used large quantities of make-up and cleansing creams.

Diffuse facial erythema and follicular plugs, which impart a ‘nutmeg grater’ appearance to the skin

Skin scrapings contained unusually large numbers of Demodex

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CLINICAL FEATURES• 2) ROSACEA-LIKE ERUPTION

Rosacea merely provides Environment for multiplication of the mites, or whether the mites play a role in initiating the disease.

?Local, delayed hypersensitivity response to Demodex antigens - inflammatory component of rosacea

Bacterial antigens associated with Bacillus oleronius, isolated from D. folliculorum, stimulate inflammatory response in PapuloPustular rosacea

Extrafollicular Demodex or fragments of Demodex may be found in the granulomatous lesions of rosacea – immune-mediated destruction and extrusion of mite remains

Mite identified from Papulo-Pustular Rosacea but not from Pustular Acne

Response to Miticidal agents, not to Metronidazole

CLINICAL FEATURES• Implicated in papular and papulopustular lesions in

immunosuppressed indls - Leukemia / MF / HIV-positivity

• Facial lesions attributed to Demodex have been described in immunocompetent children

• D. folliculorum density in perioral dermatitis suggested that increased mite density was a secondary phenomenon related to topical steroids, and also showed that mite density increased significantly in relation to the length of treatment

• Presence in Eyelash follicles has been implicated in the pathogenesis of blepharitis

OTHER ASSOCIATIONS

• Fungal spores and Mycobacterium leprae within Demodex mites – Vectors ??

• LMDF

• SEBORRHOEIC DERMATITIS

• GROVER’S DISEASE

• AGA

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DDx

• Rosacea (Papulo-Pustular)• Acne Vulgaris• Eosinophillic Folliculitis• Hydroa Vacciniforme• Folliculitis• LMDF• Trichoepithelioma / Syringoma

• Phthiriasis Pubis (Eyelids)

DIAGNOSIS

• Direct Microscopy / KOH Mount of expressed pilosebaceous contents by Comedone Extractor

• Skin Surface Biopsy

• Skin Biopsy

SKIN SCRAPING

TREATMENT

• Cleansing with Soap / Water• Miticidal agents – Benzoyl Benzoate / Lindane

1%• BPO 5%• Precipitated Sulphur 5%• Permethrin 1% X 10 mins• Ivermectin 0.5% Lot X 10 mins• Ivermection Oral – Off label in Blepharitis

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