Evaluation of Malassezia yeast colonization rate in patients with seborrheic dermatitis

Background: Seborrheic dermatitis (SD) is a chronic dermatitis with 1-3% prevalence and even with 33-83% in immunocompromised patients. Often, because of some of predisposing factors, abnormal proliferation of Malassezia yeasts (as a normal flora) is seen in patients that lead to observation of clinical symptoms in their bodies. The aim of this study was to evaluate of Malassezia yeasts colonization rate in patients with seborrheic dermatitis that has key importance to appropriate treatment. Methods: This descriptive cross-sectional study was carried out during one-year period from January 2015 to February 2016 on 45 patients. According to the sample size formula, after visiting by a dermatologist and refer to the Medical Mycology Laboratory, Tehran University of Medical Sciences, patients were subjected to mycological examinations schedules. After recording the clinical symptoms and their specifications, sampling from all patients' lesions was performed with sterile scalpel and a piece of scotch tape. Direct smears were prepared with 10% potassium hydroxide as a fungal clearing solution (KOH) and stained with methylene blue. The presence and rate of Malassezia yeast colonization was determined according to the standard procedures by direct microscopic examination. Results: From a total of 45 under studied patients, 66.7% had moderate to severe colonization of Malassezia yeast. In existence of sweating and stress factors, severe colonization with significant differences was seen (P< 0.05). In 8 cases (17.7%), mycelium form of yeast was observed. The highest mycelium observation was seen in existence of stress with significant differences (P< 0.05). Conclusion: In most of patients, yeast colonization rate was more than mild status, that emphasize on the etiological role of Malassezia yeasts at least as exacerbating factor in seborrheic dermatitis. On the other hand, the role of factors such as sweating and stress in inducing of severe colonization and invasive form of Malassezia yeasts in SD was confirmed, that should be considered to be treated as well as SD in therapeutic procedure.