Demodicidosis on the arms of a patient with pemphigus foliaceus
Authors: Bo Ri Kim, Hyun Sun Park, Hyun-sun Yoon, Soyun Cho
Journal: Journal of the American Academy of Dermatology (2014)

To the Editor: Demodex mites are common commensals of the human pilosebaceous follicle that use sebum as nourishment.1Baima B. Sticherling M. Demodicidosis revisited.Acta Derm Venereol. 2002; 82: 3-6Crossref PubMed Scopus (159) Google Scholar They are most frequently found on the face, where the number of sebaceous glands is greatest, but they have also been observed on the ear canal, scalp, neck, back, chest, nipples, buttocks, and penis.2Vance J.C. Demodectic mite on an extremity.Arch Dermatol. 1981; 117: 452Crossref PubMed Scopus (5) Google Scholar To our knowledge, there is only 1 case report of demodectic mites on the extremities (legs).2Vance J.C. Demodectic mite on an extremity.Arch Dermatol. 1981; 117: 452Crossref PubMed Scopus (5) Google Scholar Here we report a case of demodicidosis on the arms. A 56-year-old Korean man presented with a several-day history of multiple pustules localized on both arms. The lesions were asymptomatic. Pemphigus foliaceus was diagnosed by skin biopsy 2 years earlier and he had been undergoing various immunosuppressive treatments such as mycophenolate mofetil (MMF), oral corticosteroid, antihistamine, topical corticosteroids, and topical calcineurin inhibitors in the 2 years since the diagnosis. At the time of the initial appearance of the arm lesions, the patient was on 360 mg of MMF and 6 mg of methylprednisolone intermittently for 2 months. The lesions seemed to increase in number with oral intake of MMF and decrease with discontinuation. Physical examination revealed numerous discrete 2- to 3-mm erythematous follicular papules and pustules on both antecubital fossae (Fig 1). A potassium hydroxide preparation of scrapings from the erythematous pustules and scales showed the presence of many Demodex mites (Fig 2). We diagnosed this case as a Demodex infestation in a patient with pemphigus foliaceus. Treatment was successful, albeit slow, over 3 months, with twice-daily applications of topical metronidazole and benzene hexachloride to the affected areas. We could not use ivermectin because it is not available in Korea.Fig 2Potassium hydroxide scraping from Demodex folliculitis of antecubital fossa. (Original magnification: ×50.)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Demodex mites are considered normal skin fauna, and there is no consensus to what degree the mites are causative of skin pathology and how they might contribute to disease.1Baima B. Sticherling M. Demodicidosis revisited.Acta Derm Venereol. 2002; 82: 3-6Crossref PubMed Scopus (159) Google Scholar In general, Demodex mites are thought to play a pathogenic role when present in large numbers or with penetration into the dermis.3Martinez-Diaz G.J. Clark K.M. Vasquez J.G. English 3rd, J.C. Facial erythematous annular plaques: a case of annular Demodex facial dermatitis?.J Am Acad Dermatol. 2012; 67: e268-e269Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar In specific environments such as immunologic deficiency, they can proliferate and provoke cutaneous lesions.4Luebbers H.T. Lanzer M. Graetz K.W. Kruse A.L. Demodicidosis: an uncommon erythema after cranio-maxillofacial surgery.Br J Oral Maxillofac Surg. 2013; 51: e267-e268Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar The patient had previously taken a variety of immunosuppressive drugs for pemphigus foliaceus treatment, which could be an important predisposing factor for an increase in the number of Demodex mites on unusual sites. One of the multiple effects of MMF on the immune system is an inhibition of T-lymphocyte proliferation,5Zwerner J. Fiorentino D. Mycophenolate mofetil.Dermatol Ther. 2007; 20: 229-238Crossref PubMed Scopus (75) Google Scholar which can lead to mite invasion and development of clinical symptoms.4Luebbers H.T. Lanzer M. Graetz K.W. Kruse A.L. Demodicidosis: an uncommon erythema after cranio-maxillofacial surgery.Br J Oral Maxillofac Surg. 2013; 51: e267-e268Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar Demodicidosis can present in the extremities. Therefore, demodicidosis should be included in the differential diagnosis of erythematous or pustular follicular eruptions of the extremities, particularly in patients with immunodeficiency.