The diagnosis of juvenile myelomonocytic leukemia (JMML) was based on the fulfilling these criteria: (1) absence of Philadelphia chromosome or BCR/ABL fusion gene; (2) peripheral blood monocytosis > 1× 109/L (peripheral blood monocyte count: 9.2×109/L, peripheral blood lymphocyte count: 8.2×109/L); (3) less than 20% blasts (including promonocytes) in the blood and bone marrow; (4) immature granulocytes and nucleated red cells in the peripheral blood; (5) white blood cell count > 10×109/L (peripheral white blood cell count: 23.9 × 109/L); (6) splenomegaly. The gene discussed is BCR; the disease is juvenile myelomonocytic leukemia.