Clinical importance of Demodex folliculorum in patients receiving phototherapy

Abstract

Patients with immunodeficiency are prone to infestation with Demodex folliculorum mites. Ultraviolet (UV) radiation can lead to immunosuppression and sebaceous gland hyperplasia. Although some cases of demodicidosis related to UV radiation exposure have been reported, no studies have been performed on the incidence of D. folliculorum and its clinical characteristics in patients receiving phototherapy. Objective To investigate the effects of phototherapy on the density of D. folliculorum infestation and its clinical characteristics. This was a cross-sectional study. Forty-five patients receiving phototherapy and 43 age- and sex-matched healthy controls were enrolled to the study. The sociodemographic characteristics, occupational information, and skin types (2, 3, 4, or 5) of both patients and controls were carefully recorded. The dermatologic diseases requiring phototherapy, type and number of phototherapy treatments, and cumulative UV doses of all patients were noted. The clinical findings that may relate to demodicidosis were recorded. Standardized skin surface biopsies were taken from three anatomic regions (forehead, cheek, and nasal dorsum) and suspected lesions; five or more D. folliculorum mites per square centimeter of skin was defined as demodicidosis. Twelve (26.7%) patients received psoralen plus UV-A (PUVA) and 33 (73.3%) received narrow-band UV-B. Demodicidosis was detected in 13 (28.9%) patients and three (7%) controls. The difference in the demodicidosis rate between patients and controls was statistically significant (P = 0.01). In eight of the 13 patients (61.5%) with demodicidosis, clinical demodicidosis was present. Demodicidosis was present in seven of the 12 patients (58.3%) receiving PUVA and in six of the 33 patients (18.2%) receiving narrow-band UV-B. The difference in demodicidosis rates between patients receiving PUVA and those receiving narrow-band UV-B was statistically significant (P = 0.02). A statistically significant difference was also found between the mean D. folliculorum densities of patients and controls in all anatomic regions. Demodicidosis should be included in the differential diagnosis of facial eruptions in patients receiving phototherapy.