| Disease | JCML is a chronic myeloproliferative disorder that typically affects young children: more than 95% of cases are diagnosed before age 4 |
| Phenotype / cell stem origin | evidence exists for leukemic involvement of CD34-positive stem cells and monocyte-macrophage, erythroid, and B-lymphoid lineages in cases with cytogenetic abnormalities |
| Epidemiology | annual incidence is estimated to be roughly 4/million; median age 1-4 yrs; sex ratio: 1.4M/1F |
| Clinics | splenomegaly, lymphadenopathy, and skin rash are common; typical peripheral blood findings include leukocytosis (usually less than 100 x 109/L), monocytosis, and thrombocytosis with variable degree of left shift; myeloblasts average about 5% of total nucleated cells; elevation of fetal hemoglobin (hbF) very common; absence of the Philadelphia chromosome in all cases proposed clinical criteria from the International Juvenile Myelomonocytic Leukemia Working Group includes: 1. white blood cell count > 13 x 109/L (corrected for nucleated red blood cells)
2. absolute monocyte count > 1 x 109/L (corrected)
3. presence of immature myeloid precursors (myelocytes, promyelocytes, and myeloblasts) in the peripheral blood
4. bone marrow aspirate revealing < 30% blasts
5. no Ph chromosome on cytogenetic assessment
about 15% of cases are associated with neurofibromatosis type 1 ( NF-1 mutation) |
| Pathology | blood: leukocytosis, monocytosis, left shift in myeloid maturation, circulating mucleated red blood cells bone marrow: hypercellular marrow with mildly increased M:E ratio (typically 5:1), dispersed erythroid elements, and decreased numbers of megakaryocytes; dyplasia is usually not prominent |
| Treatment | intensive chemotherapy and all trans retinoic have not been shown to induce durable remissions; complete remissions have been achieved with stem cell transplantation |
| Prognosis | the disease is uniformly fatal when treated with conventional chemotherapy; among those who undergo bone marrow transplantations, the majority ultimately relapse, with an overall survival rate of 25% |
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