The first evidence that septins may contribute to human disease occurred with the discovery of SEPT5 (CDCREL-1) as a carboxy-terminus fusion partner with mixed-lineage leukemia (MLL) in an acute myeloid leukemia (AML) patient with a t (11; 22) (q23; q11.2) re-arrangement (16-18). The gene discussed is SEPTIN5; the disease is acute myeloid leukemia.