Translocation 11 childhood 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).Position 11q23 is the site of the mixed lineage leukemia gene - a gene so called because it has a gene expression profile different from that seen in other leukemias such as ALL and AML. Translocation affecting this gene is seen in as many as 80% of infants presenting with acute leukemia in the first 6 months of life. Infants with this type of leukemia have a particularly poor prognosis (outlook). They have high white blood counts and a high frequency of central nervous system involvement. 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. Translocation frequency at the MLL site declines with age and may be found in as few to 3% to 4% of adults with acute leukemia. Conventional chromosome analysis may miss this finding and molecular studies involving FISH (fluorescence in situ hybridization) methodology may be needed to detect it. MLL positive for translocation is a distinct entity separate from ALL, and requires other more aggressive therapies for treatment.
