Myelodysplastic syndrome (MDS) in children is often associated with chromosomal anomalies and trisomy 8 is a characteristic karyotypic feature in up to 20% of the cases. Behçet disease is a rare multisystem inflammatory disorder characterized by recurrent mouth and genital ulcers. MDS with trisomy 8 has been observed in adult patients with Behçet syndrome with some cases developing prior to the clinical manifestations of the latter. We present a female with a similar association and explain the importance of identifying the coexisting conditions. The immunological abnormalities, which may be observed in MDS and their possible mechanisms, are also discussed. Pediatr Blood Cancer 2008;50:649–651. © 2006 Wiley-Liss, Inc.