The Clinical Importance of Demodex folliculorum Presenting with Nonspecific Facial Signs and Symptoms

Demodex folliculorum (D. folliculorum), found in the pilosebaceous unit, is the most common ectoparasite of humans. Various clinical forms such as pustular folliculitis, papulopustular scalp eruptions, perioral dermatitis, and blepharitis have been defined, although in general, the disease has been classified into three main groups as "pityriasis folliculitis", "rosacea-like demodicidosis", and granulomatous rosacea-like "demodicidosis gravis". Our aim was to test for the presence of D. folliculorum in pathogenic numbers in patients who came to our clinic with non-specific symptoms such as facial itching with or without erythema, seborrheic dermatitis-like or perioral dermatitis-like lesions, papulopustular lesions, and an acneiform clinical appearance without telengiectasia or flushing. Twenty-eight (87.5%) female and 4 male (12.5%), patients and 33 age-and-sex matched healthy subjects enrolled in this study. D. folliculorum was sought in the lesion sites using the non-invasive method known as the Standardised Skin Surface Biopsy (SSSB). The discovery of more than five parasites in an area of 1 cm2, was evaluated as pathogenic. For treatment, 5% permethrine cream was applied twice daily for 15 to 30 days. The clinical symptoms of the patients were classified into clinical groups and evaluated as facial itching in 2 (6.3%), nonspecific erythema and itching in 21 (65.6%), erythema and pityriasiform squamous lesions in 3 (9.4%), acneiform in 3 (9.4%), papulopustular lesions in 1 (3.1%), granulomatous rosacea-like in 1 (3.1%), and perioral dermatitis-like symptoms in 1 (3.3%), D. folliculorum density was determined as 5>D/cm2 in all clinical lesions. A significant clinical healing and density of D. folliculorum at <=5 D/cm2 was determined in all but two patients after treatment. We consider that D. folliculorum presentation with different symptoms and signs than classical forms is not rare. For this reason, we suggest that it is useful to test for D. folliculorum in patients with non-classical presentations like facial itching, itching accompanied by non-specific erythema, itching and non-specific pityriasiform squamous lesions, and acneiform lesions.