PracticalDermatology

Demodex, a genus of the family Demodicidae, is a host-specific, obligate commensal microorganism that is a normal inhabitant of hair follicles and sebaceous glands of the skin. Two species have been identified in humans: Demodex folliculorum and Demodex brevis.¹ Demodicosis is the term used when the organism becomes amensal and complicit in inflammatory skin diseases. Here, we present two cases of secondary demodicosis at the background of rosacea and one case of pityriasis folliculorum, all of which are successfully treated with 10% potassium hydroxide (KOH) dermabrasion.

Case report

Patient 1 is a 50‐year‐old male patient, with a complaint of foul-smelling, painful, and purulent papulonodules on the facial area for 15 years, with remissions and relapses. Dermatological examination revealed several erythematous, follicular papules, and nodulocystic lesions mostly on the malar region, ala nasi, tip of nose and forehead. (Picture 1) Dermoscopic examination revealed Demodex follicular openings with multiple Demodex “tails,” on a background of diffuse erythema. Histopathologic analysis showed dense perivascular and perifollicular lymphoplasmacytic infiltrate with foci of neutrophilic pustules within the follicles, numerous intrafollicular Demodex mites, perifollicular non-caseating granuloma, and mild sebaceous hyperplasia. With these findings, the patient was diagnosed with granulomatous rosacea with demodicosis. One month after the first session of KOH treatment, more than 50 percent decrease in lesion density was achieved (Picture 2). At the three-month follow-up, almost all symptoms disappeared without any recurrence.

Picture 1. Pretreatment, follicular papules, and nodulocystic lesions on erythematous background.

Picture 2. a-c. post-treatment appearance during the three months duration. One month after the first session of KOH dermabrasion (a). One month after the second session of KOH treatment (b). Third month follow-up, after a total of two sessions KOH dermabrasion (c).

Patient 2 is 58-year-old otherwise healthy male patient presenting with a complaint of recurrent facial lesions for 25 years. Scaly patches were found over an erythematous background with acneiform papulopustules on the forehead, nose, malar region, and chin, with accompanying rhinophyma. Hematoxylin and eosin staining of biopsies revealed follicular dilatation and multinucleated histiocytes with numerous Demodex mites in perifollicular inflammatory infiltrate. The patient was diagnosed with phymatous rosacea with secondary demodicosis. Two sessions of KOH treatment spaced three weeks apart yielded a more than 90 percent reduction in the density of facial lesions. At three‐month follow‐up, improvement was sustained (Picture 3).

Picture 3. a-b. pre-and post-treatment appearance of facial area. Pretreatment, papulopustules with a background erythema and marked rhinophyma (a,b). Third month follow-up visit, after a total of two sessions KOH dermabrasion (c).

Patient 3 is 62-year-old male with pinpoint papules and redness all over his face for over 30 years. Skin eruption consisted of papules and pustules that coalesced on the cheeks to form plaques associated with diffuse erythema, edema, and pityriasis-like scales. Cultures from pustules for bacteria, dermatophytes, or yeast were negative. Skin biopsy showed moderate to dense perivascular and perifollicular lymphohistiocytic infiltrate with neutrophils. Excessive Demodex mites in follicular infundibula was observed. The patient was diagnosed with demodex folliculorum folliculitis. Three sessions of KOH dermabrasion were applied at an interval of four weeks. At three‐month follow‐up examination, a dramatic response was obtained, and only mild telangiectasia was detected.

Discussion

Demodicosis is not considered as a single dermatological condition. Many inflammatory skin diseases and clinical pictures, such as rosacea, pityriasis folliculorum, folliculitis, and blepharitis, have been attributed to this mite. Although direct causation has not been established yet, many studies put forward a strong association between Demodex mites and rosacea.² In two of our cases, elimination of demodicosis showed rapid resolution of their complaints, which could also demonstrate the role of Demodex in development of rosacea. In case of pityriasis folliculorum, even higher mite concentration than rosacea has been reported.³ Demodicosis can also occur in other rarer clinical settings, including perioral dermatitis, ocular rosacea, or granulomatous rosacea, as in our first case.⁴

Standardized skin surface biopsy is the preferred method for diagnosis, with highest sensitivity for detection of mites.³ Other potential diagnostic tools include dermoscopy, KOH analysis, and confocal laser scanning microscopy.^5,6 In our case series, we used both the dermoscopical examination and skin surface biopsy. Diagnosis is made by identifying more than five mites/cm² in a low-power field together with characteristic histopathological findings.

There is no consensus standard of care for the treatment of demodicosis because evidence-based trials are lacking. There are many local therapy options such as permethrin, lindane, crotamiton, or benzyl benzoate. Presence of diffuse lesions or underlying immunosuppression may require systemic treatment, and anti-parasitic drugs such as metronidazole, ornidazole and ivermectin as well as tetracycline group anti-bacterials can be used.^7,8

Due to the chronic course of the disease and resistance to previous therapy options, dermabrasion with KOH was planned for our three cases. KOH is an inorganic compound and has a prototypical strong base with caustic nature. In medical practice, it is used in the diagnosis of fungal infections, bacterial vaginosis (Whiff test), or treatment of genital warts and molluscum lesions.⁹ KOH solution is prepared at a concentration of 10% in distilled water, mixed for one to two minutes for homogenous dispersion. The solution is applied to patient’s face immediately after preparation, starting from the area where the lesions are most concentrated.

As the action starts, Demodex mites effervesce toward the surface, and they are mechanically debrided with the help of a forceps. According to tolerability of the patient and facial mite density, in five to 10 minutes, neutralization process with 0.9% saline solution is implemented for the next 15 minutes. After the procedure is complete, cold compress and Centella asiatica extract are applied to enhance epithelization and for the relief of discomfort. Patients are advised for strict sun protection after the procedure.

When the clinical trials and meta-analysis are all considered, there is no one gold standard therapy option for the treatment of demodicosis with optimal long-term efficacy and safety profile. KOH has shown to be an effective alternative for three resistant cases in this report, with recalcitrant disease and heavy Demodex load. This novel treatment option was well-tolerated in our patients, with mild and temporary side-effects, such as irritation and erythema on the application site for a few days. The effect started as early as two weeks after the procedure and patients remained symptom- and mite-free at the third month of therapy, usually with only two to three cycles of application.

KOH dermabrasion seems to be a convenient and cost-effective method for treatment of facial demodicosis, which does not require long-term, repeated applications and has better side-effect profile compared with the current treatment options. The only downside of this treatment seems to be the necessity of in-office application, under the supervision of a professional.

However, short-term treatment effects may not correlate to a chronic maintenance treatment plan for patients with recurring inflammatory conditions associated with Demodex mites, as in our three cases. More mechanistic information with future controlled clinical trials comparing the efficacy of KOH dermabrasion with other treatment options are required for evaluation of its potential, especially for those patients who have failed currently recommended treatments such as metronidazole.

These cases were originally presented during the Resident’s sessions at Cosmetic Surgery Forum (CSF) 2021. It is one of the top 10 talks selected from among the 30 resident talks given at the conference.

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