OBJECTIVE To study the clinical, histopathological and therapeutic features of Sweet syndrome with myelodysplastic syndrome (MDS). METHODS The clinical data of 3 patients with Sweet syndrome and MDS diagnosed at Peking Union Medical College Hospital between October 1988 and November 2015 were reviewed. The laboratory test results, histopathological findings, and therapeutic regimens of these patients were analyzed retrospectively. RESULTS The three cases were 29, 49 and 49 years old, respectively, including 2 females and 1 male. Two patients presented with Sweet syndrome before the onset of MDS, the other one patient developed Sweet syndrome and MDS simultaneously. The rash of all of these patients manifested as red painful papules in face, trunk and limbs, as well as edematous plaques and nodules. Histopathological examination of skin confirmed the diagnosis of Sweet syndrome. Complete blood count showed cytopenia of at least one lineage. Bone marrow cytology showed dysplasia of hematopoietic cells with abnormal high proportion of myeloblasts. Bone marrow pathology results were normal in 2 patients, while hypoplasia of hematopoietic tissue with excess adipose tissue was found in 1 patient. All the patients were treated with corticosteroid or immunosuppressants and skin lesions alleviated. But relapse was common in process of corticosteroid reduction. CONCLUSIONS Sweet syndrome may be a precursor of MDS. The clinical manifestations, histopathological and hematological findings of these rare cases are characteristic. Corticosteroid indicates short-term response. The patients who had recurrent skin lesions should be further examined to exclude MDS.