Recent progress in gene therapy for hematological disorders is reviewed. The pioneering work to correct adenosine deaminase (ADA) -deficient lymphocytes with a recombinant retrovirus, started in 1990, was successful and opened an era of genetic intervention. However, early clinical trials with similar vectors targeting hematopoietic stem cells have been problematic. In these trials, hematopoietic stem/progenitor cells were collected from the patients with monogenic disorders such as ADA deficiency, chronic granulomatous disease, Fanconi anemia, and Gaucher disease and subsequently incubated with murine leukemia virus-based vectors ex vivo. The manipulated cells were infused into the patients, and transgene expression was periodically evaluated. In most cases, functionally corrected cells were detected at very low frequencies, and they diminished over time. A much more efficient vector system is required to produce clinically relevant numbers of transduced cells with durable transgene expression. One possible approach to this goal is to expand the gene-modified hematopoietic cells in vivo. We have developed a novel system for the expansion of transduced cells by using fusion molecules between the granulocyte colony-stimulating factor receptor and the steroid-binding domains. Cells expressing the chimeric receptors proliferated in a hormone-dependent manner, which suggested that this approach is a feasible way to selectively expand transduced hematopoietic cells. As for hereditary coagulopathies, a promising approach to provide the blood coagulation factor IX has been launched very recently. In this trial, a factor IX-expressing adeno-associated virus vector is intramuscularly injected into hemophilia B patients, expecting long-term production of the functional clotting factor ectopically.

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We clinically investigated 12 patients with necrotizing lymphadenitis encountered at our department during the past 10 years. The diagnosis of the disease was based on characteristic pathological findings by lymph node biopsy. The patients' ages at diagnosis ranged from 4 to 13 years with a male-to-female ratio of 11 : 1. There was one brother-and-sister case, and three patients had recurrent diseases. Patients tended to appear in a cluster in a single year, and six cases occurred from October to December. All patients had swelling of the cervical lymph node, and the duration of fever higher than 38deg;C was from 3 to 39 days. Four of 7 cases that received minocycline achieved clinical improvement. Immunological examination at the patients' acute phases revealed a negative tuberculin test, increased levels of serum IL-6 and IFN-γ, and impaired leukocyte chemotaxis. The inversion of the ratio of CD4/CD8 (less than 1.0) in peripheral blood was observed in 2 patients, but none showed a decrease of lymphocyte blast formation to PHA. Since comprehensive reports of necrotizing lymphadenitis in childhood are quite limited, this investigation is useful for understanding the pathogenesis of this disease.

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We studied the results of 38 children with acute lymphoblastic leukemia who were treated with stem cell transplantation. Twenty of them received stem cell transplantation at the first remission, 8 at the second or third remission, and 10 at relapse. Twelve patients, including 7 who received at the first remission, recurred from 3 months to 40 months after transplantation. Disease-free survival rates of patients who received at the first remission, at the second/third remission, and at the relapse were 49.9%, 46.9%, and 50.0%, respectively. Philadelphia chromosome and myeloid antigen positive leukemia were suspected as risk factors. Severe graft-versus-host disease might lead to a low frequency of relapse. Conditioning regimens with melphalan administration had relatively good antileukemic effects. Relatively lower relapse rates were obtained at relapse with employing unrelated bone marrow transplantation or double stem cell transplantation.

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We report a 9-year-old male patient with Philadelphia positive acute lymphoblastic leukemia who received peripheral blood stem cell transplantation (PBSCT) from his one locus mismatched mother. Acute graft versus host disease (GVHD) did not appear, but he experienced late onset noninfectious pulmonary complications, which may have been due to chronic GVHD. After pulsed steroid therapy, he had no complaints. Four hundred and fifty days after the transplantation, he remains free of disease. There is insufficient information about PBSCT from one locus mismatched related donors, but in our case, the results are similar to those of BMT from one locus mismatched related donors. Because it is suspected that the transplantation of allogeneic PBSCs instead of BM can enhance the GVL effect, and that the relapse rate of allo-PBSCT may be lower than that of allo-BMT, allogeneic PBSCT may be a useful method for the high risk group, even if donors are one locus mismatched related ones.

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We report an 8-month-old boy with Hurler syndrome treated with unrelated cord blood transplantation (UCBT) from an HLA one-locus mismatched female donor. The conditioning regimen of transplantation consisted of busulfan (35 mg/m² × 4/day × 4 days), cyclophosphamide (50 mg/kg × 4 days) and antithymocyte globulin (ATG, 2.5 mg/kg × 4 days). The number of infused nucleated cells in cord blood was 4.2 X 10⁷/kg body weight. The neutrophil count of peripheral blood reached > 500/, μ1 on day 15 and platelet count > 50 × 10³/y1 on day 56. Three months after UCBT, the patient showed mixed hematopoietic chimerism in peripheral blood (donor type 78.6% and recipient type 21.4%). The proportion of the chimerism was stable even 12 months after UCBT. Neither acute nor chronic GVHD was developed. The levels of leukocyte α-iduronidase and urinary excretion of glucuronic acid were almost within normal limits after UCBT. UCBT could be a choice of treatment in patients with Hurler syndrome, who need early hematopoietic stem cell transplantation and have no HLA-matched family donors.

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We report an infant with Down syndrome associated with transient abnormal myelopoiesis (TAM), born from a t (21 ; 21) Robertsonian translocation carrier mother. On admission, skin rash developed on the whole body, especially her trunk, and the peripheral white blood cell count (WBC) was 219, 700/, μ1 with 92% blast cells. The chest X-ray showed cardiomegaly and the ultrasonography of the heart revealed pericardial effusion. The blast cells gradually subsided from the age of 35 days and finally disappeared in peripheral blood at the age of 50 days. Skin rash and pericardial effusion diminished with the decreasing of peripheral blast cells. However, brain infarction probably because of hyperviscosity of leukocytosis was found. The hypothesis of “disomic homozygosity” of a mutant gene on chromosome 21 in 21-trisomic cells has been proposed regarding a mechanism responsible for the occurrence of TAM. But we haven't found a report of a Down syndrome with TAM born from a t (21 ; 21) Robertsonian translocation carrier. It may be that our case is important for the study of a mechanism responsible for the occurrence of TAM.

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Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare disease characterized by thrombocytopenia and absence of megakaryocytes in the bone marrow and evolves to aplastic anemia. Recently, the abnormal expression of c-mpl, thrombopoietin receptor, in marrow mononuclear cells (MNC) from the patient with CAMT has been reported. We report here a 10-year-old boy who was initially diagnosed as idiopathic thrombocytopenic purpura (ITP) at the age of 3. Contrary to typical cases of ITP, he had atypical features : Absence of megakaryocytes in BM examinations and ineffective response to various therapies such as prednisolone and high-dose immunoglobulin. During the clinical course, the hemoglobin level decreased gradually by 9 years old. c-mpl mRNA was not detected in bone marrow cells of the patient despite the expression of c-kit mRNA. The serum thrombopoietin level (18.08 fmole/ml) was significantly higher than that of healthy control. The diagnosis of CAMT with evolution to aplastic anemia was made from these findings. At the age of 10, he underwent an unrelated donor umbilical cord blood transplant.

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