Myelodysplastic syndromes: the pediatric point of view

Myelodysplastic syndromes (MDS) are clonal disorders of the multipotent hematopoietic stem cell characterized by ineffective hematopoiesis and associated with marrow hypercellularity, increased intramedullary cell death and peripheral cytopenias of varying severity. Patients with myelodysplasia have a propensity (20% to 30% of cases) to undergo transformation into acute myeloid leukemia (AML), and a large body of evidence indicates that MDS represent steps in the multiphasic evolution of AML. Progression of the disease is characterized by expansion of the abnormal clone and inhibition of normal hematopoiesis leading to deterioration of the blood cell count and/or development of AML. MDS are relatively unusual in childhood, representing only 3% of pediatric hematological malignancies, although it has been reported that up to 17% of pediatric AML cases may have a previous myelodysplastic phase. The first systematic attempt at morphological classification of MDS was provided by the French-American-British (FAB) group. However, the FAB classification of MDS is only partially applicable in children. Some variants are extremely rare or absent (refractory anemia with ring sideroblasts and chronic myelomonocytic leukemia), and other peculiar pediatric disorders, represented by juvenile chronic myelogenous leukemia (JCML) and the monosomy 7 syndrome, are not included. Moreover, since there is a partial overlap between pediatric MDS and myeloproliferative disorders and the variants occurring in young children have rather specific features, some confusion still surrounds the nosographical definition of childhood MDS, so that none of the proposed classifications are widely accepted and used. Characteristically, some genetic conditions such as Fanconi's anemia, Shwachman's and Down's syndromes predispose to the development of MDS in childhood. The most common variants of childhood MDS are represented by JCML and the monosomy 7 syndrome, both disorders typically occurring in young children. JCML is characterized by a spontaneous growth of granulocyte-macrophage progenitors that show a striking hypersensitivity to granulocyte-macrophage colony-stimulating factor. Clinical presentation resembles that of some myeloproliferative disorders, with massive organomegaly usually not observed in the classically reported variants of MDS. Clinical features of the monosomy 7 syndrome resemble those observed in JCML and a differential diagnosis between these two entities relies upon the higher percentage of fetal hemoglobin, the more pronounced decrease in platelet count and, in some cases, the lack of the peculiar cytogenetic abnormality in the latter. With the number of children being cured of cancer constantly rising, a significant increase in secondary or chemotherapy-related myelodysplasia is being observed, and these disorders represent a formidable challenge for pediatric hematologists due to their poor response to chemotherapy

Recombinant human granulocyte-macrophage colony stimulating factor (rHuGM-CSF) in cyclic neutropenia

We describe the case of a 12-year-old boy affected by cyclic neutropenia, at high risk of developing life-threatening infections, treated with recombinant human granulocyte-macrophage colony stimulating factor (rHuGM-CSF). The drug was effective in reducing the severity of neutropenia and infectious complications in our patient. It was administered for brief periods of time, in contrast to the daily continuous administration reported for rHuG-CSF. Therefore, more extensive studies must be performed to identify the most effective time schedule for the drug. In vitro studies of hemopoietic progenitor cells were useful, in this case, to predict treatment response

Rhabdomyosarcoma with primary osteolytic lesions simulating non-Hodgkin's lymphoma

We report the case of an 8-year-old child presenting with the pathological fracture of two vertebral bodies due to bone lytic lesions. Physical and instrumental examinations did not show any further evidence of disease. However, bone marrow aspirate showed an infiltrate of poorly differentiated cells. When the child was transferred to the Department of Pediatrics, lymphoblastic leukemia was suspected. Although the morphology of the bone marrow biopsy could have suggested a lymphoblastic lymphoma, further immunochemical and immunological studies together with the study of tissue surface antigens resulted in a diagnosis of embryonal rhabdomyosarcoma with an unusual presentation

Transplantation of cord blood progenitor cells can promote bone resorption in autosomal recessive osteopetrosis

Allogeneic BMT has been reported to be the only curative therapy for children with juvenile autosomal recessive osteopetrosis. We report the case of a 14-month-old child in whom bone resorption was observed after cord blood transplantation (CBT). The patient was given CBT from an unrelated newborn matched for five of six HLA antigens. At the time of transplantation, the child presented with neurological symptoms, with feeding problems and visual impairment. A successful engraftment of donor hematopoiesis was demonstrated and the child experienced grade I acute GVHD. Progressive bone clearing was achieved and a bone marrow trephine demonstrated signs of osteoclast function. Despite full engraftment and bone resorption, neurologic deterioration did not improve. This experience documents that CBT can promote the correction of juvenile osteopetrosis. The shorter time needed both to identify an unrelated donor and to perform the transplant, as well as the lower incidence of GVHD make this procedure more appealing than BMT in children lacking an HLA-compatible relative

Role of allogeneic bone marrow transplantation from HLA-identical sibling or matched unrelated donor in the treatment of children with juvenile chronic myeloid leukemia

Seven children (age range 1.8-11 years) with juvenile chronic myelomonocytic leukaemia (JCML) received an allogeneic bone marrow transplantation (BMT), four from an HLA-identical sibling and three from a matched unrelated donor. In the four children transplanted using an HLA-identical sibling, conditioning regimen included busulfan (BU), cyclophosphamide (CY) and melphalan (L-PAM), whereas graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine-A (Cs-A). The preparative regimen was well tolerated and all patients engrafted promptly. None of the patients have relapsed and all four children remain in haematological remission after an observation time of 7, 24, 25 and 48 months, respectively. Of the three children given BMT from an unrelated volunteer, one was < 2 years of age and she received the BU/CY/L-PAM regimen. In view of the increased risk of graft rejection described in patients transplanted from unrelated donors, we chose to prepare the other two patients with fractionated total body irradiation (TBI), thiotepa and CY. Cs-A, short-term methotrexate and Campath-1G in vivo were employed to prevent GVHD in this group of patients. Graft failure with autologous reconstitution of haemopoiesis occurred in the child given the chemotherapy-based regimen. One of the two girls given TBI relapsed after BMT; therefore only one of the three patients who received a marrow transplant from a matched unrelated donor survives in complete haematological remission 10 months after BMT. Our study suggests that the conditioning regimen we employed for allogeneic BMT from a compatible sibling is an effective means of eradicating the leukaemic clone. In our experience, results obtained using unrelated donors are less satisfactory and, at present, the use of such donors seems to be riskier and associated with a lower success rate as compared with BMT from an HLA-identical sibling