Childhood translocation 11 leukemia: A new type of childhood leukemia in which a piece of chromosome 11 has been translocated (broken off and attached itself to another chromosome). Children with this type of leukemia have a particularly poor prognosis (outlook). They usually have very high white blood counts and a high frequency of central nervous system disease. They do not respond at all well to the standard therapies for ALL (acute lymphoblastic or lymphocytic leukemia) and often suffer from early relapse after chemotherapy. Translocations affecting chromosome 11 at position 11q23affect the mixed lineage leukemia (MLL) gene. MLL+ acute leukemia has a different gene expression profile from that of ALL and AML- hence its name. Frequency of the MLL+ state is as high as 80% in infants with acute leukemia who are less than 6 months of age, and is still relatively common at 6 months to 1 year of age. After that its frequency decreases with increasing age though it may still affect 3% to 4% of adults with acute leukemias. The translocation is not always easy to detect on conventional chromosome analysis and other techniques may be needed. MLL+ or chromosome 11 childhood leukemia is a distinct entity, and is not a subset of ALL. It requires variations on conventional treatment approaches.