Multiple leukemic clones in acute leukemia of childhood.

Two abnormal karyotypes representing clonal populations have been demonstrated in three patients in the early stage of acute leukemia. The karyotypes were apparently unrelated in one patient, while in the other two, a relationship was conjectured. Both clones were present before therapy in two patients. Although a clone resistant to therapy was associated with relapse in one case, in two cases a clone has persisted in the lymphocyte culture during drug treatment with the patients in remission.