Behçet's syndrome is a systemic vasculitis. Gastrointestinal involvement in Behçet's syndrome complicated by myelodysplastic syndrome represents a rare and severe subtype for which no standardized treatment guidelines currently exist, posing significant challenges in clinical practice. Ustekinumab, a biologic agent targeting IL-12/IL-23, has demonstrated favorable efficacy in both gastrointestinal Behçet's syndrome and inflammatory bowel disease. This study aims to evaluate the efficacy and safety of ustekinumab in patients with intestinal Behçet's syndrome and coexisting myelodysplastic syndrome.