Long-term outcome of patients with acquired chronic pure red cell aplasia (PRCA) following immunosuppressive therapy: a final report of the nationwide cohort study in 2004/2006 by the Japan PRCA collaborative study group.

Immunosuppressive therapy has been employed as the initial treatment for acquired chronic pure red cell aplasia (PRCA), such as idiopathic, thymoma-associated, or large granular lymphocyte (LGL) leukaemia-associated PRCA, which is thought to be immune-mediated. To explore the overall long-term outcome following immunosuppression and to identify the risk factors for death in these disorders, we conducted nationwide surveys in Japan 2004 and 2006, and identified a total of 185 patients with acquired chronic PRCA, including 72 idiopathic, 41 thymoma-associated and 14 LGL leukaemia-associated cases of PRCA for whom data was available. The present study evaluated 127 patients with these three subsets of PRCA. The median overall survival has not yet been reached in idiopathic PRCA. The estimated median overall survival times in patients with thymoma-associated and LGL leukaemia-associated PRCA were 142·1 and 147·8 months, respectively. Twenty-two deaths were reported, and the response to induction therapy and relapse of anaemia were found to be associated with death. The major causes of death were infection in seven patients and organ failure in another seven patients. The results suggest that maintenance therapy and the management of infectious complications are crucial for improving the prognosis of chronic PRCA.

Gain-of-function of mutated C-CBL tumour suppressor in myeloid neoplasms.

Acquired uniparental disomy (aUPD) is a common feature of cancer genomes, leading to loss of heterozygosity. aUPD is associated not only with loss-of-function mutations of tumour suppressor genes, but also with gain-of-function mutations of proto-oncogenes. Here we show unique gain-of-function mutations of the C-CBL (also known as CBL) tumour suppressor that are tightly associated with aUPD of the 11q arm in myeloid neoplasms showing myeloproliferative features. The C-CBL proto-oncogene, a cellular homologue of v-Cbl, encodes an E3 ubiquitin ligase and negatively regulates signal transduction of tyrosine kinases. Homozygous C-CBL mutations were found in most 11q-aUPD-positive myeloid malignancies. Although the C-CBL mutations were oncogenic in NIH3T3 cells, c-Cbl was shown to functionally and genetically act as a tumour suppressor. C-CBL mutants did not have E3 ubiquitin ligase activity, but inhibited that of wild-type C-CBL and CBL-B (also known as CBLB), leading to prolonged activation of tyrosine kinases after cytokine stimulation. c-Cbl(-/-) haematopoietic stem/progenitor cells (HSPCs) showed enhanced sensitivity to a variety of cytokines compared to c-Cbl(+/+) HSPCs, and transduction of C-CBL mutants into c-Cbl(-/-) HSPCs further augmented their sensitivities to a broader spectrum of cytokines, including stem-cell factor (SCF, also known as KITLG), thrombopoietin (TPO, also known as THPO), IL3 and FLT3 ligand (FLT3LG), indicating the presence of a gain-of-function that could not be attributed to a simple loss-of-function. The gain-of-function effects of C-CBL mutants on cytokine sensitivity of HSPCs largely disappeared in a c-Cbl(+/+) background or by co-transduction of wild-type C-CBL, which suggests the pathogenic importance of loss of wild-type C-CBL alleles found in most cases of C-CBL-mutated myeloid neoplasms. Our findings provide a new insight into a role of gain-of-function mutations of a tumour suppressor associated with aUPD in the pathogenesis of some myeloid cancer subsets.

[Survey on examinations for diagnosis of bone marrow failure in Japan: a report from the Japanese National Research Group on Idiopathic Bone Marrow Failure Syndromes].

Using a registration sheet of a prospective registration system for aplastic anemia (AA)/myelodysplastic syndromes (MDS), by the National Research Group on Idiopathic Bone Marrow Failure Syndromes, Japan, we carried out a survey on examinations for diagnosis of bone marrow failure. Bone marrow trephine biopsy was performed in 66 of 105 cases (63%) [Original diagnosis: AA 51 cases (80%), MDS 12 (32%), undiagnosable 3 (75%)]. Bone marrow aspiration was performed in all cases, and aspiration was performed at least twice in 36 cases (34%). The first-line anatomic site for bone marrow aspiration was the posterior iliac crest (62%). Cytogenetic examination was performed in 93%. The concordance rate between the original and the central review diagnosis was 93% among the studied cases: AA, Idiopathic cytopenia of undetermined significance (ICUS) and MDS in total. Flow cytometry analysis to detect paroxysmal nocturnal hemoglobinuria (PNH)-type blood cells was performed in 32%.

Long-term effect of the complement inhibitor eculizumab on kidney function in patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a debilitating and life-threatening disease in which lysis of PNH red blood cells frequently manifests with chronic hemolysis, anemia, and thrombosis. Renal damage in PNH is associated with chronic hemosiderosis and/or microvascular thrombosis. We determined the incidence of renal dysfunction or damage, defined by stages of chronic kidney disease (CKD), in a large cohort of PNH patients and evaluated the safety and efficacy of the complement inhibitor eculizumab in altering its progression. Renal dysfunction or damage was observed in 65% of the study population at baseline with 21% of patients with later stage CKD or kidney failure (glomerular filtration rate [GFR]

Molecular cloning of t(2;7)(p24.3;p14.2), a novel chromosomal translocation in myelodysplastic syndrome-derived acute myeloid leukemia.

In this study, we report the molecular structure of the breakpoint region in a new chromosomal translocation, t(2;7)(p24.3;p14.2), in a case of acute myeloid leukemia transformed from myelodysplastic syndrome (MDS). An extensive fluorescence in situ hybridization (FISH) analysis showed that NAG (2p24.3) and ELMO1 (7p14.2) were involved at the breakpoints of t(2;7)(p24.3;p14.2). Furthermore, we detected a novel chimeric transcript consisting of NAG and ELMO1. Interestingly, this transcript encoded a truncated molecular form of 3'ELMO1 as the result of a frameshift caused by the chromosomal translocation. Although this study does not provide direct evidence that a defect in NAG-ELMO1 plays a role in the pathogenesis or the leukemic change in MDS, it does suggest that defects in NAG-ELMO1 potentially contributed to the leukemic progression in this case.

The impact of cytogenetic abnormalities on the prognosis of primary myelofibrosis: a prospective survey of 202 cases in Japan.

Cytogenetic abnormalities were often observed in primary myelofibrosis patients. The presence of specific cytogenetic abnormalities, such as sole abnormalities of chromosome 13q-, 20q-, or -7/7q-, is reported to have the influence on the prognosis of primary myelofibrosis. We analyzed the data from the prospective survey of Japanese primary myelofibrosis patients which was conducted from 1999 to clarify the impact of cytogenetic abnormalities on the prognosis of primary myelofibrosis. A total of 202 primary myelofibrosis patients had the cytogenetic and the prognostic data. Eighty (40%) out of 202 cases had cytogenetic abnormalities, and an association was evident for platelet counts. Although the presence of an abnormal karyotype did not affect the prognosis, primary myelofibrosis patients with cytogenetic abnormalities other than 13q- and 20q- showed an inferior prognosis compared to patients with a normal karyotype or sole 13q- or 20q- abnormalities. Patients with an unfavorable cytogenetic profile (abnormal cytogenetics other than 13q- or 20q-) also had a greater tendency to transform to leukemia than patients with a favorable cytogenetic profile (normal cytogenetics, sole abnormalities of either chromosome 13q-, or 20q-). Abnormal cytogenetics other than 13q- or 20q- in primary myelofibrosis patients has the poor prognostic effect for both survival and the risk of leukemic transformation.

Cut-off value of red-blood-cell-bound IgG for the diagnosis of Coombs-negative autoimmune hemolytic anemia.

Direct antiglobulin test (DAT)-negative autoimmune hemolytic anemia (Coombs-negative AIHA) is characterized by laboratory evidence of in vivo hemolysis, together with a negative DAT performed by conventional tube technique (CTT) in clinically suspected AIHA patients. The immunoradiometric assay (IRMA) for red-blood-cell-bound immunoglobulin G (RBC-IgG) can be used to diagnose patients in whom CTT does not detect low levels of red cell autoantibodies. We investigated the diagnostic cutoff value of the IRMA for RBC-IgG in Coombs-negative AIHA and calculated its sensitivity and specificity. Of the 140 patients with negative DAT by CTT referred to our laboratory with undiagnosed hemolytic anemia, AIHA was clinically diagnosed in 64 patients (Coombs-negative AIHA). The numbers of Coombs-negative AIHA and non-AIHA patients changed with age and gender. The cutoff values were determined from receiver operating characteristic (ROC) curve according to age and gender. The IRMA for RBC-IgG proved to be sensitive (71.4%) and specific (87.8%) when using these cutoffs. Using these cutoffs for 41 patients with negative DAT referred to our laboratory in 2006, all the pseudonegative cases were treated with steroids before the test. The 31 untreated cases could be grouped using one cutoff value of 78.5 and showed 100% sensitivity and 94% specificity, independent of gender and age. Results indicate that RBC-IgG could become a standard approach for the diagnosis of Coombs-negative AIHA, when measured before treatment.

Acquired pure red cell aplasia associated with malignant lymphomas: a nationwide cohort study in Japan for the PRCA Collaborative Study Group.

Pure red cell aplasia (PRCA) has been reported in association with lymphoma as one of the autoimmune diseases seen during the course of lymphoid malignancies. However, the relation of PRCA with the underlying lymphomas remains unclear. The aim of this study was to clarify the histologic subtypes of lymphomas, the chronological sequence of anemia and lymphoma, and the response to treatment. We conducted a nationwide survey in Japan. From a cohort of 185 PRCA patients, 8 patients with lymphoma were evaluated. Histologic subtypes varied and the lymphoma was of the B-cell type in four cases and of the T-cell type in four. Four patients simultaneously developed PRCA and lymphoma. Three patients developed PRCA following lymphoma, two of whom developed anemia during remission of lymphoma. PRCA preceded lymphoma in one patient. Effective chemotherapy was associated with remission of anemia in concurrent lymphoma and PRCA. Overall, anemia responded to chemotherapy and/or immunosuppressive therapy in seven patients. In four responding patients, PRCA remained in durable remission without maintenance immunosuppressive therapy, which is different from a recurrent feature of idiopathic PRCA. We suggest that the mechanism of lymphoma-associated PRCA is heterogeneous and that durable maintenance-free remission of anemia can be obtained in some patients.

Long-term response and outcome following immunosuppressive therapy in thymoma-associated pure red cell aplasia: a nationwide cohort study in Japan by the PRCA collaborative study group.

BACKGROUND: Thymoma-associated pure red cell aplasia (PRCA) accounts for a significant proportion of cases of secondary PRCA and immunosuppressive therapy has been reported to be useful in this condition. However, because of its rarity, the long-term response and relapse rates after immunosuppressive therapy are largely unknown, and optimal management of this disorder remains unclear. The aim of this study was to collect more information on the outcome of patients with thymoma-associated PRCA. DESIGN AND METHODS: We conducted a nationwide survey in Japan. From a total of 185 patients, comprising 73 with idiopathic and 112 with secondary PRCA, 41 patients with thymoma were evaluated for this report. End-points of this study were the response rate, duration of the response after immunosuppressive therapy and overall survival. RESULTS: Surgical removal of thymoma was reported in 36 patients, 16 of whom developed PRCA at a median of 80 months post-thymectomy. First remission induction therapy was effective in 19 of 20 patients treated with cyclosporine, 6 of 13 patients treated with corticosteroids and 1 of 1 treated with cyclophosphamide. No cyclosporine-responders relapsed within a median observation period of 18 months (range; 1 to 118 months). Relapse of anemia was observed in three corticosteroid-responders who did not receive additional cyclosporine. Only two patients were in remission after stopping therapy for 19 and 67 months. The estimated median overall survival time of all patients was 142 months. CONCLUSIONS: Thymoma-associated PRCA showed an excellent response to cyclosporine and cyclosporine-containing regimens were effective in preventing relapse of anemia. It does, however, remain uncertain whether cyclosporine can induce a maintenance-free hematologic response.

Long-term responses and outcomes following immunosuppressive therapy in large granular lymphocyte leukemia-associated pure red cell aplasia: a Nationwide Cohort Study in Japan for the PRCA Collaborative Study Group.

Large granular lymphocyte leukemia-associated pure red cell aplasia accounts for a significant portion of secondary pure red cell aplasia cases. However, because of its rarity, long-term responses and relapse rates after immunosuppressive therapy are largely unknown. We conducted a nationwide survey in Japan and collected 185 evaluable patients. Fourteen patients with large granular lymphocyte leukemia-associated pure red cell aplasia were evaluated. Cyclophosphamide, cyclosporine A and prednisolone produced remissions in 6/8, 1/4 and 0/2 patients respectively. Seven and 5 patients were maintained on cyclophosphamide or cyclosporine A respectively. Two patients relapsed after stopping cyclophosphamide, and 2 patients relapsed during maintenance therapy with cyclosporine A. The median relapse-free survival in the cyclophosphamide - and the cyclosporine A groups was 53 and 123 months respectively. Large granular lymphocyte leukemia-associated pure red cell aplasia showed a good response to either cyclophosphamide or cyclosporine A. Most patients continued to receive maintenance therapy and it remains uncertain whether cyclophosphamide or cyclosporine A can induce a maintenance-free hematologic response in large granular lymphocyte leukemia-associated pure red cell aplasia.

Pregnancy-induced hemolytic anemia with a possible immune-related mechanism.

BACKGROUND: Pregnancy-induced hemolytic anemia is a rare maternal complication that occurs during pregnancy and resolves soon after delivery. The mechanism is unclear, and the disease is often referred to as unexplained hemolytic anemia associated with pregnancy. CASE: We report a case of life-threatening hemolytic anemia that occurred during pregnancy and resolved spontaneously soon after delivery. Direct and indirect Coombs test results were negative. Several possible causes were investigated, but all were ruled out. However, an increased immunoglobulin G level was observed in maternal red blood cells throughout pregnancy when the patient was severely anemic. The immunoglobulin G level decreased after delivery and was close to the control level on postpartum day 5. CONCLUSION: These observations suggest that the hemolytic anemia in this patient had an immune-related etiology.

A safety, pharmacokinetic and pharmacodynamic investigation of deferasirox (Exjade, ICL670) in patients with transfusion-dependent anemias and iron-overload: a Phase I study in Japan.

The pharmacokinetics (PK) and pharmacodynamics (PD) of the once-daily, oral ironchelating agent, deferasirox (Exjade, ICL670), have been evaluated further in a Phase I, openlabel, multicenter, dose-escalation study in Japanese patients with myelodysplastic syndromes, aplastic anemia, and other anemias. Deferasirox was initially administered as a single dose of 5 (n = 6), 10 (n = 7), 20 (n = 6) or 30 (n = 7) mg/(kg day) and then after 7 days seven daily doses were administered. Linear PK (C (max) and AUC) were observed at all doses after a single dose and at steady state, and dose-dependent iron excretion was observed. Pharmacokinetic/pharmacodynamic parameters were similar to those reported in a Caucasian beta-thalassemia cohort. Following the single- and multiple-dose phases, 21 of 26 patients progressed to a 3-year extension phase of the study, where dose reductions and increases [5-30 mg/(kg day)] were allowed following safety and efficacy assessments. In the interim, 1-year data show that deferasirox was well tolerated, with generally infrequent and mild adverse events. Reductions in serum ferritin levels were observed and a negative iron balance achieved at doses of 20-30 mg/(kg day). These data suggest that deferasirox has a stable and predictable PK/PD profile, irrespective of underlying disease or race, and a predictable and manageable safety profile suitable for chronic administration.

Danazol therapy for aplastic anemia refractory to immunosuppressive therapy.

Although there are anecdotal reports of the efficacy of danazol in the treatment of aplastic anemia (AA), there has been no systematic study to clarify its efficacy and toxicity. Therefore, we assessed the efficacy of danazol for treatment of patients with AA refractory to immunosuppressive therapy (IST) and those who relapsed after IST, in a prospective clinical trial. Sixteen patients (12 males and four females; six severe cases and 10 moderate cases) were treated with 300 mg of danazol daily for 12 weeks. All patients completed the treatment period without occurrence of severe toxicity. Three female patients achieved partial remission, whereas only two of the 12 male patients did so. None of the responders had shown a response to previous IST or an increase in the percentage of paroxysmal nocturnal hemoglobinuria (PNH)-type cells which are known to be a marker for a good response to IST. These findings indicate that danazol is effective for a subset of AA patients, and particularly for female patients with AA refractory to IST.

Roles of DRB1 *1501 and DRB1 *1502 in the pathogenesis of aplastic anemia.

OBJECTIVE: Although a number of reports have documented a significantly increased incidence of HLA-DR15 in aplastic anemia (AA), the exact role of HLA-DR15 in the immune mechanisms of AA remains unclear. We herein clarify the difference between DRB1( *)1501 and DRB1( *)1502, the two DRB1 alleles that determine the presentation of HLA-DR15, in the pathophysiology of AA. MATERIALS AND METHODS: We investigated the relationships of the patients( *) HLA-DRB1 allele with both the presence of a small population of CD55(-)CD59(-) (PNH-type) blood cells and the response to antithymocyte globulin (ATG) plus cyclosporin (CsA) therapy in 140 Japanese AA patients. RESULTS: Of the 30 different DRB1 alleles, only DRB1( *)1501 (33.6% vs 12.8%, p(c) < 0.01) and DRB1( *)1502 (43.6% vs 24.4%, p(c) < 0.01) displayed significantly higher frequencies among the AA patients than among a control. AA patients possessing HLA-DR15 tended to be old, and especially, the frequency of DRB1( *)1502 in patients 40 years of age and older (52.4%) was markedly higher than that in those younger than 40 years old (16.2%, p(c) < 0.01). Only DRB1( *)1501 was significantly associated with the presence of a small population of PNH-type cells and it also showed a good response to ATG plus CsA therapy in a univariate analysis. A multivariate analysis showed only the presence of a small population of PNH-type cells to be a significant factor associated with a good response to the immunosuppressive therapy (p < 0.01). CONCLUSIONS: Although both DRB1( *)1501 and DRB1( *)1502 contribute to the development of AA, the methods of contribution differ between the two alleles.

[Overview of the clinical reference guides for the idiopathic hematopoietic disorders].

The research committee for idiopathic hematopoietic disorders, which has been supported by the government over the past 35 years, has recently worked out a series of reference guide for the management of diseases under investigation to provide aids for better understanding of pathophysiology of diseases and appropriate clinical decision making. Such attempts covered aplastic anemia, Fanconi anemia, pure red cell aplasia, autoimmune hemolytic anemia, paroxysmal nocturnal hemoglobinuria, myelodysplastic syndromes and primary myelofibrosis, and included diagnostic criteria and severity classification as well as clinical pictures derived from nationwide survey studies. Therapeutic measures were evaluated according to the concepts of evidence-based medicine, when applicable. This report presents an overview of these guides and summarizes key issues in each disease entity.

Long-term outcome of patients with acquired primary idiopathic pure red cell aplasia receiving cyclosporine A. A nationwide cohort study in Japan for the PRCA Collaborative Study Group.

BACKGROUND AND OBJECTIVES: Cyclosporine A (CsA) has become one of the leading agents for the treatment of pure red cell aplasia (PRCA). However, further studies are necessary to determine the relapse-free survival (RFS) and overall survival (OS) of patients treated with this drug, the minimum duration of therapy for induction of remission, and whether or not there is need for maintenance treatment. DESIGN AND METHODS: We conducted a nationwide survey in Japan. From a total of 185 patients (with 73 primary idiopathic PRCA and 112 with secondary PRCA), we evaluated 62 patients with primary idiopathic PRCA for this report. RESULTS: The remission induction therapy for these patients included CsA (n=31), corticosteroids (CS) (n=20) or other drugs (n=11). CsA and CS produced remissions in 23 (74%) and 12 (60%) patients, respectively. The salvage treatment produced remissions in 58 patients (94%). Forty-one and 15 patients were maintained on CsA+/-CS (CsA-containing group) or CS alone (CS group), respectively. The median RFS in the CsA-containing group was 103 months, longer than that seen in the CS group (33 months) (p<0.01). Of 14 patients whose CsA was discontinued, 12 patients (86%) relapsed after a median of 3 months (range 1.5 to 40 months), while only 3 of 27 patients (11%) relapsed during CsA-containing maintenance therapy. Thus, the discontinuance of maintenance therapy was strongly correlated with relapse (p<0.001). Four patients in the CsA-containing group died; however, the OS of this group was not significantly different from that of the CS-groups (p=0.104). INTERPRETATION AND CONCLUSIONS: CsA-containing regimens sustain prolonged RFS more effectively than CS in primary idiopathic PRCA and seem to be important to prevent relapse.

The effect of anabolic steroids on anemia in myelofibrosis with myeloid metaplasia: retrospective analysis of 39 patients in Japan.

Between 1999 and 2005, 285 patients received new diagnoses of myelofibrosis with myeloid metaplasia (MMM) in Japan. Anemic symptoms were present in 162 patients, and hemoglobin (Hb) concentrations were <10 g/dL in 197 patients. Fifty-five MMM patients were treated with anabolic steroids, and their effect on anemia during MMM was evaluated in 39 patients. A "good" response was defined as an Hb increase of >or=1.5 g/dL, cessation of transfusion dependence, and an Hb concentration of >10 g/dL maintained for at least 8 weeks. A "minimum" response was defined as an Hb increase of >or=1.5 g/dL and transfusion independence for at least 8 weeks. Both good and minimum responses were considered "favorable." Favorable responses were achieved in 17 patients (44%, 8 good and 9 minimum responses). None of the pretreatment variables, such as the lack of transfusion dependence, a higher Hb concentration at the start of treatment, or the absence of cytogenetic abnormalities, were associated with a response to anabolic steroid therapy. Adverse events associated with anabolic steroid therapy were moderate and transient. Two patients required definitive withdrawal of treatment. Thus, anabolic steroids are well tolerated and effective for the treatment of anemia in a subset of MMM patients.

A prospective study of cyclosporine A treatment of patients with low-risk myelodysplastic syndrome: presence of CD55(-)CD59(-) blood cells predicts platelet response.

Although immunosuppressive therapy using antithymocyte globulin or cyclosporine A (CSA) is effective in selected patients with low-risk myelodysplastic syndrome, the response rates reported so far are inconsistent, and the indication of immunosuppressive therapy for myelodysplastic syndrome has not been clearly defined. We treated 20 myelodysplastic syndrome patients (17 refractory anemia cases [RA], 2 RA with excess blasts, and one RA with ringed sideroblasts) with 4 mg/kg per day of CSA for 24 weeks. Among the 19 patients evaluated, 10 showed hematologic improvement; 8 patients showed an erythroid response, 6 showed a platelet response, and one showed a neutrophil response. Most patients with hematologic improvement continued CSA thereafter, and the progressive response was observed until the latest follow-up (median, 30 months). Most toxicities associated with CSA usage were manageable, and no patient had developed acute leukemia up to this point. Short duration of illness, refractory anemia with minimal dysplasia determined by bone marrow morphology, and the presence of paroxysmal nocturnal hemoglobinuria-type cells were significantly associated with the platelet response. A minority of RA patients who did not possess such predictive variables achieved an isolated erythroid response. In conclusion, CSA may be a therapeutic option for patients with RA who do not have adverse prognostic factors.

[Clinical evaluation of biapenem for febrile neutropenia in patients with hematological disorders].

We examined the clinical evaluation of biapenem (BIPM) for febrile neutropenia in patients with hematological disorders. BIPM was administrated by drip infusion when fever developed over 37.5 degrees C with a neutrophil counts lower than 1000/microl. The underlying diseases were acute myelogenous leukemia in 16 cases, acute lymphocytic leukemia in 1, malignant lymphoma in 14, myelodysplastic syndrome in 1, aplastic anemia in 1. Microbiologically documented infections were found in 3 cases (9.1%) before treatment. Clinical effect was excellent in 9 cases, good in 11, fair in 6, poor in 7. Factors associated with efficacy rate were concomitant use of granulocytecolony stimulating factor, duration of neutropenia and neutrophil counts at day 3 of day after start of the therapy. No serious adverse events were observed in all cases, although one case developed exanthema. In conclusion, these results confirmed the efficacy and safety of BIPM for febrile neutropenia in patients with hematological disorders.

[Clinical analysis of HLA-DR-negative non-M3 AML].

The type of leukemia was defined as HLA-DR(-) non-M3-AML, when HLA antigens were detected by flow cytometry at an incidence of < 20% of the blast population excluding M3-AML. Out of 109 patients with de novo acute myeloid leukemia, 8 patients had HLA-DR(-) non-AML-M3. According to the French-American-British criteria, 7 patients could be subdivided into 3 patients with M1, 4 patients with M2 and 1 patient with M4. The morphological features of bone marrow aspiration demonstrated no dysplasia and peroxidase stain positivity was noted in over 86% of the blast cells in all patients, the blast cells with fine granularity in 7 patients. The cytogenetic analysis revealed a normal karyotype. There was no expression marker of the blast antigens except CD13, CD14, CD33, CD34 and CD56. All of 7 patients who underwent induction therapy attained complete remission. Overall survival and disease-free survival showed no significant differences between the HLA-DR(-) non- M3-AML group and the HLA-DR(+) AML group.