Abstract: Jiang Yanyun, Li Ji, Li Yue, Li Siqian, Xu Hui, Fang Kai, Jin Hongzhong, Qian Jiaming Department of Dermatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China（Jiang YY, Fang K, Jin HZ）; Department of Gastroenterology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China（Li J, Li Y, Xu H, Qian JM）; Department of Internal Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China （Li SQ） Corresponding authors: Jin Hongzhong, Email: jinhongzhong@263.net; Qian Jiaming, Email: qianjiaming 1957@126.com 【Abstract】 Objective To investigate clinical manifestations, histopathological features and treatment of ulcerative colitis（UC） complicated by pyoderma gangrenosum （PG）. Methods Data on clinical manifestations, auxiliary examination findings, treatment and prognosis were collected from 8 inpatients with UC complicated by PG in Peking Union Medical College Hospital between July 2009 and July 2016, and analyzed retrospectively. Results Of the 8 cases, 5 were male, and 3 were female. The average age of onset was 30.6 years and 35.1 years in males and females respectively. All the patients developed intestinal symptoms of UC before the onset of PG with an average time interval of 5 years. Moreover, all the patients had active total colonic type UC at the onset of PG, including 6 with moderately active UC and 2 with mildly active UC. PG manifested as painful ulcers in 8 patients, and affected lower limbs in 7 patients. Histopathological examination of skin lesions showed typical characteristics of vasculitis in 5 patients. Five patients were complicated by arthralgia. All the patients were treated with glucocorticoids and 5-aminosalicylic acid agents as the basic therapy, 3 patients received extra treatment with immuno-suppressive agents or minocycline, and 2 with infliximab. Conclusions PG is a severe skin manifestation of UC, commonly occurs in patients with total colonic type UC in the active stage, and mostly affects the lower limbs, with typical histopathological features of vasculitis.