Abstract: Zhou Xing, Lu Jinghao, Hu Dongyan, Liu Chaofan, Xin Chongmei, Zhu Lubing, Li Ming Department of Dermatology, Zhongshan Hospital, Fudan University, Shanghai 200032, China Corresponding author: Zhu Lubing, Email: Zhu lubing@ zs?hospital.sh.cn 【Abstract】 Objective To analyze clinical and pathological features of dermatomyositis with pan?niculitis as a skin manifestation. Methods Clinical data were collected from 9 cases of dermatomyositis with panniculitis as a skin manifestation in Department of Dermatology of Zhongshan Hospital affiliated to Fudan University from October 2012 to July 2016, and their clinical and pathological features were analyzed. Results Of the 9 cases, 6 were female and 3 were male, and the age ranged from 28 to 73 years. Panniculitis lesions of the 9 patients all manifested as painful indurated plaques or nodules on the buttock, thigh, waist, back, abdomen, upper extremities and cheeks. These lesions occurred before, after or simultaneously with the onset of characteristic skin and muscle lesions of dermatomyositis, especially preceded the onset of characteristic lesions of dermatomyositis by 30 years in 1 case. Histopathological examination of lesions showed liquefaction degeneration of basal cells, inflammatory infiltration of lymphocytes and plasma cells around blood vessels, in the fat lobules as well as between the lobules and septa in the dermis. The necrosis and calcification of lipocytes, lipomembranous changes, fibrinoid necrosis of damaged vessel walls and microvascular occlusion were observed in some cases. Because panniculitis preceded the onset of characteristic lesions of dermatomyositis, 2 patients were misdiagnosed with lupus panniculitis and morphea profunda for several times. Most patients had good response to systemic glucocorticoids combined with immunosuppressive agents, while the patients with lipomembranous fat necrosis had poor response to the combination therapy. Conclusions Panniculitis lesions of dermatomyositis are histologically characteristic, and may do not coincide with the onset of characteristic lesions of dermatomyositis. If panniculitis lesions precede characteristic lesions of dermatomyositis, patients will be easily misdiagnosed. Thus, persistent follow?up visit will be of great importance for the diagnosis.