Objective:To investigate the relationship of Castleman disease (CD) and connective tissue disease (CTD).Methods:Clinical records and laboratory data of 11 patientsdiagnosed with CD and CTD were collected and retrospectively analyzed. All patients were diagnosed at Peking Union Medical College Hospital.Results:① The proportion of CD associated with or mimicking CTD was 5.67% (11/194) in all CD patients during the same period. The average age of these cases at the diagnosis was (51±17) years and the ratio of male to female was 6∶5. ② Lymphadenopathy (10/11), fever (8/11), serosal effusion (6/11), arthralgia (5/11), alopecia (2/11), Raynaud phenomenon (1/11) and photosensitivity (1/11) were the common clinical manifest- ations that could mimic CTD. ③ Elevated ESR (11/11), hypoalbuminemia (11/11), elevated CRP (10/11), elevated IgG (7/11), proteinuria (5/11), hematuria (5/11) and positive ANA(5/11) were commonly found in the patients' laboratory tests. ④ CD was inclined to mimic systemic lupus erythematosus(SLE)(5/11), IgG4-related disease(IgG4-RD)(2/11) and adult onset Still's disease(AOSD)(2/11), as well as 2 cases were associated with Sj?gren's Syndrome(SS)(2/11). ⑤All cases were ultimately diagnosed as multicentric CD, the pathologic subtypes were plasma cell variant (10/11) and mixed(1/11) respectively.Conclusion:CD maybe overlapped with or mimic a variety of clinical manifestations, such as fever, serosal effusion, arthralgia and proteinuria which could mimic CTD. Early biopsy is helpful for the diagnosis and to avoid misdiagnosis and mistreatment.