Demodex folliculorum in chronic blepharitis
Department of Ophthalmology, University of Erlangen-Nürnberg (Chairman: Prof. Dr. G.O.H. Naumann)Schwabachanlage 6, D-91054 Erlangen, Germany
Background and Purpose. The mite demodex folliculorum (Class Arachnida, Order Acarina), first described by Berger in 1841, can be found in the hair follicles of the eyelashes and of the contigous facial skin. The shorter species Demodex brevis inhabits meibomian and other sebaceous glands. The live cycle of the mite is 14 ½ days. The about 300µm long adult mite lives 5 to 6 days in the follicle of the eyelash or hair, can migrate on to the skin during night time (negative phototrop) by moving 1cm per hour. The classic clinical appearance are "sleeves", 1mm long cylindrical cuffs around the base of the eyelashes. The association of demodex with diseases like blepharitis, lid hyperemia, meibomitis, chalazion or rosacea is controversal discussed. Also the vector capacity of demodex for bacterial infections remains unclear. The incidence of demodex is age related. It was found up to 20 years in about 25%, up to 50 years in about 30%, up to 80 years in about 50% and in all aged 90 or older. In healthy persons, one can find one or more Demodex in every tenth eyelash. This index rise with increasing age. In blepharitis or other external eye diseases, demodex is found in about every sixth eyelash. Therapy of chronic blepharitis in association with demodex may include antibiotics, steroids, Quecksilber 2% or Lindan. Massage of lidmargins is essential because local treatment is of no effect as long as the mite remains deep in the pilosebaceous complex.
Patient and Methods. A 54-year old man suffered from therapy resistent chronic blepharitis without improvement under therapy of antibiotics and/or steroids. Symptoms were itching, foreign body sensation and epiphora. There was anterior and posterior blepharitis with thickening and vasodilatation of the lid margins. On slitlamp examination, several "sleeves" at the base of eyelashes were detected. 6 eyelashes of the lower lid from both sides were epilated, transferred to a glass slide and promptly examined by lightmicroscopy.
Results. Adharent to the hair bulb of several epilated eyelashes one or two Demodex folliculorum were seen. The video shows two mites, situated with the head downwards towards the root of the eyelash. One is located between the cuticula and Huxleys layer. One can see the prosoma incorporating head and thorax (cephalothorax), provided with four pairs of legs, and the opisthosoma consisting of abdomen and tail. At the head, two lateral palps and a U-shaped formation, between the palps and behind a beak-shaped growth, move actively. The three telescopic segments of the legs move at intervals, frequently only one leg at a time. The tail moves up and down. The abdomen is filled up by granules and vacuole-like formations.
Conclusion. Epilation of eyelashes and subsequent microscopic examination is an easy and effective method for detecting demodex folliculorum. Instead the role o the mite in diseases of ocular region is uncertain, Demodex should be considered in chronic therapy resistent blepharitis. Beside of "sleeves" gnawed and stunted, easely epilated eyelashes may be clinical signs for demodex folliculorum. The higher incidence of demodex may play a pathogenic role in ocular diseases.
Literature of interest:
Anselm JünemannSchwabachanlage 6 Department of ophthalmology of university of Erlangen-Nürnberg 91054 Erlangen, Germany telefone: 09131/853001 fax: 09131/856401