Dissecting folliculitis (dissecting cellulitis) of the scalp: a 66-patient case series and proposal of classification

Background and Objectives: Dissecting folliculitis (DF) or dissecting cellulitis of the scalp is regarded as a rare disease with disfiguring scarring alopecia. This study aimed to analyze the features of DF and to propose a classification to define its severity. Patients and Methods: A hospital-based retrospective study was conducted. Patients with a histopathological diagnosis or clinical features leading to diagnosis of DF were included and classified into three stages. Results: Among the 66 patients recruited (63 men / 3 women, mean age 24.9 years), multiple interconnected alopecic nodules involving the vertex scalp were the main feature. Histopathology showed an extensive inflamed granulation abscess forming a dissection plane in the lower dermis/subcutis in the acute stage. Lymphocytic infiltration was predominant in seven of 21 histology specimens. Overweight and obesity were noted in 29 of 45 patients examined. No association with smoking was found. There was comorbidity with acne conglobata in 15 of 66 patients, two of whom had acne inversa. Longer disease duration and greater number of nodules were associated with higher severity of DF (p < 0.05). A complete remission rate of 25 % was achieved by any treatment, and a rate of 37.5 % was achieved with oral isotretinoin alone. Conclusions: DF is not uncommon in Taiwan. An association with obesity needs to be clarified.