Objectives A rare case of juvenile dermatomyositis (JDM) complicated by myelodysplastic syndrome (MDS) was reported in order to improve the understanding of the disease in its clinical signs, differential diagnosis and treatment. Meth-ods The course of the disease, clinical characteristics and the process of diagnosis and treatment were analyzed. Specimens of bone marrow, lymph nodes, muscles were examined by histopathological or immunohistopathological means and lfow cytometry. Results The diagnosis of JDM complicated by MDS was made based on the clinical manifestations, related laboratory results and the accompanying changes in hematological and bone marrow examinations. Conclusions JDM complicated by MDS is very special and rarely seen in China and its pathological mechanism and strategy of diagnosis and treatment should be further explored.