This study aimed to investigate the characteristics of Chinese patients with Behçet disease (BD) and myelodysplastic syndrome (MDS) and explore the role played by trisomy 8. This was a retrospective study of patients with BD and MDS from the Shanghai Behçet’s disease database who were diagnosed between October 2012 and July 2017. There were 805 patients with BD and 16 also had MDS. Trisomy 8 was examined in patients with BD-MDS and some patients with gastrointestinal (GI) BD. Patients with BD and MDS (16/805; 2%) were more likely to be female and older; display fever and intestinal lesions; have lower leukocyte count, hemoglobin, platelet count; and show higher C-reactive protein and erythrocyte sedimentation rate (ESR) than patients with BD without MDS (all P<0.05). Trisomy 8 was common (81.3%) in patients with BD-MDS. Ulcers in the ileocecal region were more frequently seen in intestinal patients with BD-MDS than in BD without MDS (90.0% versus 48.9%; P=0.032). GI ulceration is common in patients with BD-MDS. Cytogenetic aberrations, especially trisomy 8, may play a role in the pathogenesis of intestinal involvement in patients with BD-MDS.