These aggressive leukemia forms constitute more than 70 % of infant leukemias and about 10 % of adults’ leukemias and are associated with poor prognosis for the patients: children affected by ALL harboring this translocation have an overall survival of 50 %, whereas children with ALL that does not harbor the MLL translocation have an overall survival of over 80 % [56–59]. Here, KMT2A is linked to leukemia.