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Check the eyelashes in rosacea patients when Demodex occurs on the face

Key clinical point: All rosacea patients with Demodex on their faces had Demodex in the eyelashes, suggesting that eyelashes should be checked in any rosacea patient with Demodex on the face.

Major finding: Rosacea patients had significantly higher rates of Demodex infestation on their faces compared with controls (P = 0.007); eyelash infestation rates were similar between the groups, but the Demodex count in the eyelashes was significantly higher among rosacea patients (P =0.012).

Study details: The data come from a prospective, cross-sectional study of 40 adults with rosacea and 40 controls enrolled between April 2016 and April 2017 at a single center; 16 eyelashes were sampled from each patient and control.

Disclosures: The study received no outside funding. The researchers had no financial conflicts to disclose.

Commentary

“This study again brings up the concept of Demodex infestation in rosacea and blepharitis. The study found that there was no increase in blepharitis in rosacea patients compared to those without rosacea, but when blepharitis was present, the density of Demodex was increased. Clinically important was a significant association of Demodex infestation with the symptom of itchy eyes even in those without evidence of blepharitis. In other words, listen to your patient’s complaints and react accordingly.

I still have so many questions. Is Demodex infestation an etiologic factor for the development of rosacea or does rosacea skin provide a more hospitable microenvironment for the Demodex to flourish? Since Demodex mites are commensal organisms present in everyone, how many are too many? They are the most common obligate ectoparasite on humans, seen with an overall prevalence of 46% of eyelash samples, increasing with age (as does rosacea, BTW) to 100% in patients over 70. At what point does the presence of the mites become an infestation? Does a certain level of overpopulation tip the scale from normal ecosystem to disease? Do we only call it an infestation when it produces signs and symptoms? A glance through the ophthalmology literature reveals that blepharitis is considered an entity unto itself; review articles fail to even note rosacea as a comorbidity. But the two disorders share a common pathophysiology of innate immune system activation, triggering of inflammatory cascades resulting in chronic inflammation, the presence of an abundance of Demodex mites, good clinical response to doxycycline and increasing prevalence with increasing age. Is all blepharitis really rosacea of the eyelids? Rosacea sin skin manifestations?

I’m still confused, but I will be doing a better job of examining all of my rosacea patients with itchy eyes.”

Hilary Baldwin, MD
Medical Director, Acne Treatment and Research Center
Brooklyn, New York
Clinical Associate Professor, Robert Wood Johnson Medical Center
Newark, New Jersey

Citation:

Ogrum A and Alim S. Niger J Clin Pract. 2020 Aug 12. doi: 10.4103/njcp.njcp_590_18.