Clues to Facial Demodicidosis: A Case Illustration.

Sir,

A 46-year-old, otherwise healthy, female presented to us with burning sensation and redness on the face for the past 6 months. She denied history of flushing or photosensitivity and had not noticed any exacerbating or relieving factors. Treatment history included pimecrolimus 1% cream twice daily and sunscreens for 3 months with a suspected diagnosis of rosacea, which had led to an exacerbation of her symptoms. History was relevant for melasma, for which she had used topical steroid-containing preparations intermittently for several years. Owing to the suboptimal reduction in the pigmentation, she had resorted to heavy make-up to camouflage the hyperpigmentation. On examination, dull erythema was perceptible on the central forehead, bilateral cheeks, perioral region, and chin with minimal semi-adherent “spiny” scaling in the perioral location, giving the skin a “nutmeg grater” feel [Figure 1]. A 40% potassium hydroxide (KOH) mount prepared from the scrapings from the perioral region showed multiple Demodex mites [Figure 2]. Dermoscopic examination using nonpolarized light did not show any specific features of Demodex infestation, namely, “Demodex tails” or “Demodex follicular openings” [Figure 3]. The patient refused a skin biopsy. With a diagnosis of facial demodicidosis, the patient was treated with topical ivermectin 0.5% cream once daily for application on the affected areas and advised to stop using cosmetics and topical steroids. At 1-month follow-up, there was complete resolution of her symptoms, and clinically there was no erythema and scaling. A repeat KOH preparation from the same sites did not reveal any Demodex mites.

Figure 1

Diffuse dull erythema on the cheeks and perioral region, with fine scaling appreciable in the perioral location

Figure 2

(a) Potassium hydroxide mount showing multiple Demodex mites (arrows, ×100). (b) Under high power (×400)

Figure 3

Dermoscopic examination using nonpolarized light showing only erythema and few telangiectasias. No Demodex tails or Demodex follicular openings are seen

Demodex folliculorum and Demodex brevis are commensal mites which inhabit the pilosebaceous units in humans. However, multiplication of these mites beyond a certain limit can lead to “demodicidosis.” Its morphological variants include pityriasis folliculorum, rosacea-like demodicidosis, and demodicidosis gravis (granulomatous rosacea-like demodicidosis).[12] It is noteworthy that finding an occasional mite is not diagnostic. At present, visualization of five or more mites under a low-power field or per 5 cm2 on standardized skin surface biopsy is considered significant, but this figure is based on limited studies.[12] That is why the diagnosis of demodicidosis rests not only on finding Demodex mites in high numbers but also on the specific clinical presentation and a positive response to acaricidal agents, both clinical as well as parasitological.[13] The morphology of facial lesions in our patient fits well with the description of pityriasis folliculorum variant of facial demodicidosis. The diagnosis was confirmed by demonstration of several mites on KOH mount, and the clinical and parasitological response to topical ivermectin. Our case provided several clues to suspect demodicidosis. Although burning sensation, centrofacial erythema, and the antecedent prolonged use of topical steroids are common to both erythemo-telangiectatic rosacea as well as facial demodicidosis, the absence of flushing episodes, photosensitivity, telangiectasias tilted the diagnosis in favor of the latter. Moreover, since pimecrolimus is an effective drug for rosacea,[4] the definite worsening of symptoms with its use in our patient further raised the suspicion. Pimecrolimus has been associated with demodicidosis, probably due to its immunosuppressive action.[567] Our patient was habitually using heavy make-up which can also contribute to demodicidosis, secondary to its occlusive effect on hair follicles.[2]

To conclude, demodicidosis is often misdiagnosed as rosacea owing to their similar presentations. Subtle differentiating clues may often be overlooked in a busy practice. Differentiating between the two entities is important as some treatment modalities for rosacea can aggravate demodicidosis.

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Conflicts of interest

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