A case of Demodex folliculorum infection

Abstract

A 40-year-old female developed erythematous patches with small pustules and scales on both cheeks with itching, starting the day after total laparoscopic hysterectomy with bilateral salpingectomy performed under general anesthesia for menorrhagia. Direct microscopic examination of scales from both cheeks revealed five or more Demodex mites per field of view. Treatment with doxycycline 100 mg/day, oral ivermectin 9 mg, and other measures targeting rosacea were administered, but there was no improvement. However, improvement was observed after 20 days of treatment with oral metronidazole.In this case, the skin lesions were consistent with pityriasis folliculorum, a manifestation of skin involvement caused by Demodex mites. While the pathogenicity of Demodex mites on the skin remains a matter of debate, pityriasis folliculorum is considered to be one phenotype reflecting the immunomodulatory effect of Demodex mites. Demodicosis should be considered a differential diagnosis from conditions such as rosacea and acne vulgaris. When a large number of Demodex mites are confirmed by direct microscopic examination, it is advisable to avoid topical corticosteroid treatment in addition to administering rosacea-targeted therapy.Further research standardizing collection and evaluation methods is necessary to further understanding of the pathogenesis, treatment, and epidemiology of Demodex mites as a part of the human skin microbiota.