AFF3 and acute lymphoblastic leukemia: The AFF (AF4 (ALL1 (acute lymphoblastic leukemias)-fused gene from chromosome 4)/FMR2 (fragile X mental retardation 2)) family of genes includes four members: AFF1/AF4, AFF2/FMR2, AFF3/LAF4 and AFF4/AF5q31.