PAX5 complete loss seems to be a secondary event and is significantly associated with BCR-ABL1 or TCF3-PBX1 fusion genes and a lower white blood cell count..     ///    PAX5 mutations occur frequently in adult B-cell progenitor acute lymphoblastic leukemia and PAX5 haploinsufficiency is associated with BCR-ABL1 and TCF3-PBX1 fusion genes: a GRAALL study.. 