JMML is a myeloproliferative/myelodysplastic disorder with characteristic clinical and laboratory findings. The incidence of JMML is estimated to be approximately 0.6–1 per million children. The disease is caused by the clonal expansion of a transformed pluripotential hematopoietic progenitor, involving proliferation of the granulocytic and monocytic lineages.
We report a 3-year-old boy with NF-1, leukocytosis and hepatosplenomegaly. Blood examination revealed leukocytosis (WBC 18.1 x 109/l) with monocytosis and immature granulocytes; anemia; thrombocytopenia. Hemoglobin F was in a normal range. A bone marrow aspirate revealed increased cellularity with 35% monocytic cells and 9–13% myelo-monocytic blasts. We diagnosed JMML and 6 months later the patient underwent allo-BMT. Prednisone and cyclosporine were used for GVHD prophylaxis up to day +70. On day +85 GVHD occurred, requiring treatment with cyclosporine and prednisone. +120 bone marrow evaluations revealed clinical remission. While receiving systemic immunosuppressive therapy the patient developed disseminated L. monocytogenes infection, sepsis, meningitis and neurological deficit, as well as paralysis of the right leg. Now he has recovered and still in clinical remission.