Supplementary Material for: Clinical and Dermoscopic Features of the Scalp in 31 Patients with Dermatomyositis

Background: Scalp involvement is not directly evaluated in patients with dermatomyositis (DM). Therefore, the exact frequency of scalp dermatomyositis (SDM) and its clinical and trichoscopic characteristics have been poorly described. Objective: The aim of this study was to determine the frequency and clinical and dermoscopic features of SDM in patients diagnosed with DM. Methods: We performed a descriptive prospective, cross-sectional observational study that included all patients diagnosed with DM at a Mexican academic institute over the course of a year. Results: Twenty-four out of 31 patients with DM had scalp involvement at clinical examination, with a prevalence of 77.4%. SDM was clinically characterized by erythema in all cases, scales in 20 (83.3%) patients, nonscarring alopecia in 21 (87.5%) patients, pruritus in 17 (70.8%) patients, and poikiloderma of the scalp in 16 (51.6%) patients. Twenty-eight patients were evaluated by trichoscopy. The most consistent finding was the presence of enlarged capillaries, found in 20 (71.4%) cases, followed by peripilar casts (57.1%) and tufting and interfollicular scales in 14 (50%) cases. Twenty-two patients also had positive nail fold capillaroscopic features similar to those observed by trichoscopy. Limitations: The simple size was limited. Conclusions: Scalp involvement and alopecia are common in patients with DM, and trichoscopy shows features similar to those found at capillaroscopy. Trichoscopy is a very important tool for diagnosis of scalp involvement in patients with DM.