Comparison of haploidentical-allogeneic hematopoietic stem cell transplantation and intensive immunosuppressive therapy for patients with severe aplastic anemia with an absolute neutrophil count of zero: a retrospective study.

A retrospective analysis was conducted based on the clinical data from 60 patients older than 16 years from January 2016 to January 2021. All the patients were newly diagnosed with severe aplastic anemia (SAA) with an absolute neutrophil count (ANC) of zero. We compared the hematological response and survival of haploidentical-allogeneic hematopoietic stem cell transplantation (HID-HSCT) (n = 25) and intensive immunosuppressive therapy (IST) (n = 35) treatments. At six months, the overall response rate and complete response were significantly higher in the HID-HSCT group than those in the IST group (84.0% vs. 40.0%, P = 0.001; 80.0% vs. 17.1%, P = 0.001). With a median follow-up of 18.5 months (4.3~30.8 months), patients in the HID-HSCT group had longer overall survival and event-free survival (80.0% vs. 47.9%, P = 0.0419; 79.2% vs. 33.5%, P = 0.0048). These data suggested that HID-HSCT might be an effective alternative treatment option for adult patients with SAA with an ANC of zero, which requires further validation in an additional prospective study.

Three times spontaneous remission of severe aplastic anemia following granulocyte transfusion from related donors: a case report and literature review.

Aplastic anemia (AA) is a bone marrow failure disease caused by abnormal activation of T lymphocytes, resulting in the apoptosis of hematopoietic cells and bone marrow failure. Currently, hematopoietic stem cell transplantation (HSCT), immunosuppressive - therapy (IST), and supportive care (e.g. transfusion adjuvant therapy, hematopoietic growth factors, and prevention of infection) are the main treatments of AA. Granulocyte transfusion has recently been accepted as an useful adjuvant therapy of HSCT and intensive IST. This article reported a severe AA patient who failed to respond to IST, but achieved spontaneous remission three times after granulocyte transfusions from related donors. Such cases have rarely been reported. Existence of human leukocyte antigen (HLA) cross between the patient and his relatives may influence the T cell-mediated immunity, which might explain this patient's recovery.

[The variation and clinical significance of paroxysmal nocturnal hemoglobinuria clone in patients with aplastic anemia before and after immunosuppressive therapy].

OBJECTIVE: To evaluate the evolution of paroxysmal nocturnal hemoglobinuria (PNH) clone and its clinical significance before and after immunosuppressive therapy (IST) in patients with aplastic anemia (AA). METHODS: A total of 186 patients diagnosed as AA were enrolled in this study. Among them, 55 patients were diagnosed as severe AA (SAA) and treated with cyclosporine (CsA) plus anti-thymocyte globulin (ATG), 131 were diagnosed as non SAA (NSAA) and treated with CsA alone. All patients were screened for PNH clone by flow cytometry before treatment and followed up for 18-76 months, with a median time of 22 months. RESULTS: Positive PNH clones were detected in 10 SAA (18.9%) patients, significantly more than that of NSAA group [9 patients (7.4%), t = 5.041, P = 0.025]. The proportions of PNH clones in SAA group at 6, 12, 24 and > 24 months were 13.38%, 14.88%, 20.00% and 18.85%, respectively, also significantly higher than those of NSAA patients (5.67%, 5.31%, 5.47% and 9.08%, all P values < 0.05). Clinical response rates were comparable in both ATG+CsA or CsA alone groups no matter PNH clone was positive or negative. CONCLUSIONS: PNH clone are detectable in AA patients either treated with ATG plus CsA or CsA alone, and more significant by ATG plus CsA. Whether PNH clone occurred before or after IST does not affect the therapeutic efficacy.

[Change and significance of Th22 cells in patients with aplastic anemia].

OBJECTIVE: To explore the proportion of Th22 cells in peripheral blood of patients with aplastic anemia (AA) and evaluate its significance. METHODS: From January 2011 to June 2012, a total of 47 AA patients were recruited and divided into 4 groups: severe aplastic anemia (SAA) pre-therapy (group A, n = 11), non-severe aplastic anemia (NSAA) pre-therapy (group B, n = 12), SAA post-therapy (group C, n = 12), NSAA post-therapy (group D, n = 12) and healthy donor controls (n = 12). The proportion of Th22 cells in peripheral blood of each group was evaluated by flow cytometry. The cytokines interleukin-22 (IL-22), transforming growth factor-ß (TGF-ß), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured by ELISA. And the level of IL-22 mRNA was examined by reverse transcription-PCR (RT-PCR). RESULTS: The percentage of Th22 cells and the level of IL-22, TNF-α, IL-6 and IL-22 mRNA in group A (4.3% ± 1.4%, (57 ± 17) ng/L, (497 ± 123) ng/L, (323 ± 88) ng/L, 1.65 ± 0.51) and group C (2.6% ± 0.6%, (34 ± 10) ng/L, (314 ± 79) ng/L, (187 ± 45) ng/L, 0.92 ± 0.28) were significantly higher than that in control group (1.2% ± 0.3%, (19 ± 6) ng/L, (228 ± 50) ng/L, (134 ± 26) ng/L, 0.47 ± 0.09,all P < 0.05). The percentage of Th22 cells and the level of IL-22, TNF-α , IL-6 and IL-22 mRNA in group A were higher than those in group C (all P < 0.05). NSAA patients had similar results. The percentage of Th22 cells and the level of IL-22, TNF-α , IL-6 and IL-22 mRNA in group A were higher than those in group B (all P < 0.05). But the level of TGF-ß in groups A and C were significantly lower than that in control group ((3.4 ± 1.1) and (5.8 ± 1.7) vs (9.7 ± 2.8) ng/L, P < 0.05). And the level of TGF-ß in group A was lower than that of group B (P < 0.05). CONCLUSIONS: The number of Th22 cells is elevated in AA patients. Th22 cells may be positively correlated with the development of AA. And a higher level of TNF-α, IL-6 and a lower level of TGF-ß promote the differentiation of Th22 cells.

[Changes of transcription factors Bcl-6, Foxp3 and RORγt in CD4(+) cells in bone marrow of immuno-related hematocytopenia].

OBJECTIVE: To evaluate the possible mechanism of transcription factors B cell lymphoma 6 (Bcl-6) , forkhead/winged helix transcription factor 3 (Foxp3) and retinoic acid related orphan receptor (RORγt) in CD4(+) T cells for immuno-related hematocytopenia (IRH). METHODS: CD4(+) T cells were harvested from 40 IRH patients, 38 aplastic anemia subjects and 25 normal controls and separated by magnetic activated cell sorting (MACS). Then the expressions of transcription factors of Foxp3, RORγ and Bcl-6 in CD4(+) T cells were measured by real time fluorescent quantitative-polymerase chain reaction (QRT-PCR). RESULTS: Auto-antibody was detected on CD34(+) cells (67.5% (27/40) ), CD15(+) cells (65.0% (26/40)), GlyA(+) cells (75.0% (30/40) ), auto-antibody involving three, two or one myeloid cell were detected in 27.5% (11/40), 52.5% (21/40), 20.0% (8/40) of IRH patients. Compensatory increase of Foxp3 mRNA was found in IRH (0.124 (0.073-0.198) vs 0.071 (0.046-0.118), P < 0.05). The expression of Bcl-6 was higher (2.243 (0.854-4.544) vs 1.211 (0.131-2.816), P < 0.05). Compared to aplastic anemia, the expression of RORγt was lower in IRH (0.133 (0.068-0.189) vs 0.290 (0.138-0.480), P < 0.01) and the ratio of Treg/Th17 shifted to Th17 in patients with aplastic anemia (Foxp3/RORγt ratio,0.500 (0.240-0.795) vs 0.975 (0.483-1.416), P < 0.01). CONCLUSION: As one kind of bone marrow failures caused by autoantibody to bone marrow cells, IRH may occur due to a high expression of Bcl-6 in CD4(+) T cells, its immunopathogenesis is different from that of aplastic anemia.

[Impact of induced therapy before allogeneic hematopoietic stem-cell transplantation for higher-risk myelodysplastic syndrome: experience of single centre].

OBJECTIVE: To explore the impact of prior-to-transplantation induction therapy (IT) on patient outcome after allogeneic hematopoietic stem-cell transplantation (Allo-HSCT) for higher-risk myelodysplastic syndromes (MDS). METHODS: A total of 49 consecutive patients underwent Allo-HSCT for MDS between November 2002 and December 2012. Twenty-six lower-risk MDS cases received supportive therapy (ST). And 17/23 cases of higher-risk MDS received IT prior to transplantation while another 6 only with ST. Their survival, relapse rate and incidence of transplantation-related mortality (TRM) were retrospectively analyzed according to International Prognostic Scoring System (IPSS) scores and marrow blast count. RESULTS: The 5-year cumulative overall survival (OS), disease-free survival (DFS), relapse rate and incidence of transplantation related mortality (TRM) were 59.9%, 59.2%, 10.5% and 31.8% during a median follow-up period of 24.4 (6.2-72.0) months. The OS and DFS of higher-risk group with IT, ST and lower-risk group were different (72.1% vs 16.7% vs 68.1%, P = 0.028; 72.1% vs 16.7% vs 67.9%, P = 0.030). And the OS and DFS of higher-risk group with IT were similar to those of lower-risk group (P = 0.526,0.504) . For the higher-risk group, the patients on IT had improved survival than those on ST in terms of OS and DFS (both P = 0.020). Moreover, the OS and DFS of remission group were higher than non-remission group in patients on IT (both 100% vs 46.7%, P = 0.049). The number of marrow blasts significantly decreased after IT (P = 0.010) without increased TRM (28.9% vs 33.6%, P = 0.612). CONCLUSION: Induction therapy prior to Allo-HSCT for MDS may reduce clone burden and improve the outcomes of higher-risk MDS without increased TRM.

[Lower risk myelodysplastic syndrome patients with transfusion dependent treated by dose-reduced decitabine].

OBJECTIVE: To evaluate the efficacy and safety of dose-reduced decitabine for the lower risk myelodysplastic syndrome (MDS) patients with transfusion dependent. METHODS: Twenty-five cases of lower risk (low or intermediate-1 risk in IPSS risk group) MDS patients with transfusion dependence from November 2009 to September 2012 were treated by dose-reduced decitabine (20 mg/m(2) intravenously once daily for 3 days). And their efficacy, side effects, quality-of-life and survival rate were evaluated. RESULTS: Among them, the responses included complete remission (CR, n = 3, 12%), transfusion independence (n = 4, 16%), hematologic improvement (HI, n = 8, 32%) and stable disease (SD, n = 2, 8%). And the overall response rate (ORR) was 68% (17/25) . Among 11 cases available for cytogenetic evaluation, 1 achieved partial cytogenetic remission (PRc). IV grade hematologic toxicity rate was 48% (12/25) and III-IV grade infection rate 20% (5/25). No severe hematologic toxicity was observed. After treatment, the Karnofsky performance score (KPS) increased from 47 ± 16 to 66 ± 22 (P = 0.001); more patients were reclassified as WPSS ≤ 1 (44%vs 16%, P = 0.031) or MDACC score ≤ 7 (64% vs 8%, P = 0.022). The median follow-up time was 467(14-881) d. The 100 and 600-day expected survive rates of low and intermediate -1 risk in IPSS risk group were 100% versus 95.2% and 100% versus 90.5%. CONCLUSIONS: Dose-reduced decitabine is well-tolerated and effective in transfusion dependent MDS patients in IPSS-lower risk. There is a low rate of severe hematologic toxicity and early mortality. It may prolong their survival time.

[Retrospective analysis on therapeutic effect of autologous hematopoietic stem cell transplantation in multiple myeloma patients].

OBJECTIVE: To evaluate the efficacy and prognostic factors of autologous hematopoietic stem cell transplantation (ASCT) in multiple myeloma (MM) patients. METHODS: Retrospective analysis was performed in 27 MM patients undergoing ASCT at our hospital from May 2004 to August 2011. After comparing with 28 patients achieving very good partial response (VGPR) or better outcome and not undergoing ASCT, the impact on the extent of response, progression-free survival (PFS) and overall survival (OS) as well as related prognostic factors of MM patients were analyzed. RESULTS: All patients successfully underwent hematopoietic reconstruction without transplantation-related mortality. The complete remission (CR) rate of ASCT group increased from 25.9% (7/27) at pre-ASCT to 70.4% (19/27) at post-ASCT (P < 0.01). The estimated 5-year rate of progression-free survival was 56.2% (median not reached) in the ASCT group and 24.9% (median 29 months) in the non-ASCT group (P < 0.05). The 5-year probability of overall survival was 52.2% (median not reached) in the ASCT group and 33.1% (median 60 months) in the non-ASCT group (P > 0.05). Univariate analysis in ASCT group demonstrated that maintenance/consolidation therapy was associated with PFS (P = 0.010) and OS (P = 0.008).Patients on induction therapy containing bortezomib and early ASCT maintenance therapy all survived without disease progression until final follow-up (P = 0.010). CONCLUSIONS: ASCT can further increase the CR rate, prolong PFS and probably OS. The incorporation of novel agents into induction, consolidation and maintenance phases has optimized the anti-myeloma activity of ASCT and may be important for improved long-term outcomes.

[Clinical efficacies and safety of HAG regimen for patients with high-risk myelodysplastic syndromes: a multicentre study].

OBJECTIVE: To evaluate the efficacies and toxicity of HAG (HHT + Ara-C + G-CSF) regimen in patients with high-risk myelodysplastic syndromes (MDS). METHODS: A total of 97 patients with high-risk MDS received HAG regimen as the induction therapy. RESULTS: The complete remission (CR) rate of all the patients was 52.3% (45/86). The overall response (OR) rate was 66.3% (57/86). The early mortality rate was 9.3% (9/97). There was no significant difference in CR rate and OR rate between the patients aged ≥ 60 and those < 60. The OR rate was 29/34, 9/12 and 6/13 in patients with favorable karyotype, intermediate karyotype and unfavorable karyotype respectively. The OR rate was higher in patients with favorable karyotype than those with unfavorable karyotype (P = 0.038). The major adverse effect was infection. CONCLUSION: HAG regimen provides higher CR rate and OR rate for patients with high-risk MDS.

Frontline Therapy Options for Adults With Newly Diagnosed Severe Aplastic Anemia: Intensive immunosuppressive Therapy Plus Eltrombopag or Matched Sibling Donor Hematopoietic Stem Cell Transplantation?

Severe aplastic anemia (SAA) is a life-threatening bone marrow failure disease. Allogeneic hematopoietic stem cell transplantation from a matched sibling donor (MSD-HSCT) and intensive immunosuppressive therapy (IST) are 2 major comparable treatments for SAA. As the addition of eltrombopag (EPAG) to standard IST therapy has greatly improved the survival prognosis of SAA, whether MSD-HSCT or IST/EPAG is the better choice has become a matter of debate. A study was performed involving 99 patients with newly diagnosed acquired SAA from 5 medical centers, including 48 MSD-HSCT cases and 51 IST/EPAG cases, which consisted of rabbit antithymocyte globulin or porcine-antilymphocyte globulin, cyclosporine plus eltrombopag. The results suggested that patients treated with MSD-HSCT or IST/EPAG had similar overall survival (OS) rates exceeding 95% (P = .97). However, the event-free survival rate (EFS) of IST/EPAG (71.0%) was significantly lower than that of MSD-HSCT (89.6%), P = .04. Subgroup analysis indicated that the OS of the MSD-HSCT group was superior to that of the IST/EPAG group (100% versus 85.7%, P = .04) among those with very severe aplastic anemia (VSAA). Both the complete response rate (CR) and overall response rate (OR) with MSD-HSCT were significantly higher than those with IST/EPAG (CR: 79.2% versus 15.7%, P < .001; OR: 97.9% versus 72.6%, P = .001). In conclusion, IST/EPAG or MSD-HSCT treatment achieves an equally high OS in SAA, but MSD-HSCT leads to a better OS in patients with VSAA and shows advantages in improving EFS and accelerating hematopoietic reconstruction in patients with SAA.

Decitabine as a treatment choice for de novo acute basophilic leukemia: transient response-a case report.

Acute basophilic leukemia (ABL), as a rare form of acute myeloid leukaemia (AML) accounts for <1% of cases of AML. ABL has not been detected for encouragingly specific targets. Here we report a de novo fragile ABL case treated with decitabine based regimen with transient response even if overall survival was a 3-month. The case of a 79-year-old male who was complained of fever, rashes and cytopenia is reported in the current study. The diagnosis of ABL was identified due to characteristic cytomorphological features and immunophenotype of myeloid blast cells without the Philadelphia chromosome. The patient initially presented with short-term improvement with decitabine. Combination of decitabine and arsenic trioxide in second chemotherapy regimen didn't reverse the end of death with a 3 months overall survival. In conclusion, our study revealed that decitabine may be an efficient therapeutic option in ABL patients and warranted much more exploration in use.

[Clinical Characteristics and Bone Marrow Histopathology Features in Essential Thrombocythaemia Patients with Different Gene Mutation in China].

OBJECTIVE: To investigate the clinical characteristics, laboratorial and bone marrow pathological features of primary thrombocytopenia (ET) patients with different mutations of CALR, JAK2 and MPL genes. METHODS: The chinical data of 120 cases of ET in Jiangsu provincial people's hospital/ The First Affiliated Hospital of Nanjing Medical University from January 2015 to December 2017 were collected and analyzed, including 76 cases with JAK2 gene mutation, 40 cases with CALR gene mutation, 2 cases with MPL gene mutations, 2 cases without gene mutation. RESULTS: Among the ET patients, compared with the JAK2 gene mutation, CALR gene mutation showed statistically significant deareament of white blood cells and hemoglobin (P=0.001, P=0.01) and the male platelets in CALR group showed significant increament (P=0.04). Fourthermore, the average number of megakaryocytes and its cluster numbers in each hight power field of vision showed statistically significant decreament in CALR group as compared with JAK2 group (P=0.001, P=0.001), and thrombotic events in CALR group were signicantly lower than those in JAK2 group (7.5% vs 18.4%) (P=0.03). CONCLUSION: Mutations of CALR, JAK2 have different clinical characteristics and blood pathological changes of Chinese ET patients, and their clinical significance is worth to explore.

Outcomes of CAG regimen for refractory biphenotypic acute leukemia patients.

OBJECTIVE: To evaluated the efficiency of low-dose cytosine arabinoside plus aclarubicin with concurrent administration of granulocyte colony-stimulating factor (CAG) regimen for refractory biphenotypic acute leukemia (BAL). METHODS: We treated 5 refractory BAL patients by CAG regimen (10 mg x m(-2) cytosine arabinoside subcutaneously administrated every 12 hours, day 1-14; 5-7 mg x m(-2) aclarubicin intravenously administrated daily, day 1-8; and concurrently used 200 microg x m(-2) x d(-1) granulocyte colony-stimulating factor subcutaneously) from November 2002 to April 2007. The efficacy of the regimen was evaluated by response rate, and the side effects were also measured. RESULTS: The complete remission rate was 80%, median duration of absolute neutrophil count < 5.0 x 10(8)/L and platelet count < 2.0 x 10(10)/L was day 13 and day 1, respectively; and the infection rate was low (III-IV infection rate, 20.00%). CONCLUSION: CAG regimen as remission induction chemotherapy for BAL patients is effective with a high remission rate and low toxicity.

Clinical outcomes of immunosuppressive therapy for severe aplastic anemia patients with absolute neutrophil count of zero.

Objectives: To evaluate the prognosis of adult severe aplastic anemia (SAA) patients with absolute neutrophil count (ANC) values of zero prior to immunosuppressive therapy (IST). Methods: Patients with ANC values of zero prior to IST were separated from very SAA and analyzed in a prospective study. All patients received IST with rabbit anti-thymocyte globulin (ATG) and cyclosporine (CsA). Results: A significantly lower response rate (RR) was identified in patients with ANC = 0 prior to IST when compared to patients with SAA after both 3 and 6 month periods or compared to those with vSAA at 3 months only. The efficacy of IST was inversely related to ANC = 0. The overall survival rate of the 'zero' group was significantly lower than that of the vSAA or SAA groups. Overall survival was closely associated with response to IST, and was inversely related to ANC = 0. Discussion: In SAA patients, ANC is associated with prognosis, the elucidated overall survival improvement in patients without ANC = 0 occurred in conjunction with decreased infection-related mortality. Our study revealed that adult patients with ANC = 0 prior to IST responded poorly to IST, suggesting that having a very low number of neutrophils was a highly predictive factor for efficacy and survival of SAA patients treated with IST. Conclusion: Adult SAA patients with ANC = 0 had a very poor prognosis and new therapeutic regimens may result in better outcome for these patients.

Assessment of clonality in T-cell large granular lymphocytic leukemia: flow cytometric T cell receptor Vß repertoire and T cell receptor gene rearrangement.

The usefulness of flow cytometric variable ß-chain repertoire (FC-Vß) and T-cell receptor gene rearrangement (TCR-GR) analyses for differentiating T-cell large granular lymphocytic leukemia (T-LGLL) from reactive T-large granular lymphocyte (T-LGL) lymphocytosis has been insufficiently studied to date. In this study, we analyzed the diagnostic value of TCR-GR and FC-Vß analysis in T-LGLL, and compared these results. In our study, FC-Vß analysis was positive in all cases of T-LGLL, and clonality assessment of FC-Vß had equal sensitivity and specificity to GeneScanning analysis but was more sensitive than heteroduplex analysis. Suspected T-cell clonality can best be addressed by evaluating two TCR targets (TCRß and TCRγ), either in parallel or consecutively. Signal transducer and activator of transcription 3 (STAT3) mutation may provide a diagnostic tool for classifying some cases of T-LGL lymphocytosis as true T-LGLL. Our results further demonstrate a significant correlation of STAT3 mutation with pure red cell aplasia, neutropenia, hepatomegaly, ß2-microglobulin and anemia.

Transformation of myelodysplastic syndromes into acute myeloid leukemias.

BACKGROUND: Myelodysplastic syndromes (MDSs), also called preleukemias, are a group of myeloid hematopoietic malignant disorders. We studied the transformation of MDS into acute myeloid leukemia (AML). METHODS: Leukemic transformation in 151 patients with MDS was dynamically followed up. The clinical manifestation, peripheral blood and bone marrow condition, karyotypes, immunophenotypes, response to treatment, and prognosis of AML evolution from MDS (MDS-AML) were also observed. RESULTS: During the course of this study, over the past eight years and seven months, 21 (13.91%) of 151 MDS patients progressed to overt leukemia, with a median interval of 5 (1 - 23) months. There were no significant differences between rates of leukemic transformation in comparison with the refractory anemia (RA), RA with excess of blasts (RAEB), and RAEB in transformation (RAEB-t) patient groups. Transformation occurred either gradually or rapidly. There were five parameters positively correlated to leukemic transformation: under 40 years of age, pancytopenia of 3 lineages, more than 15% blasts in the bone marrow, at least two abnormal karyotypes, and treatment with combined chemotherapy. All of the 21 patients with leukemia suffered from MDS-AML, and most of them were M2, M4, or M5. Two (9.52%) MDS-AML patients developed extramedullary infiltration. Leukopenia was found in 47.62% of these patients. Two thirds of these patients, whose bone marrows were generally hypercellular, suffered from neutropenia. After developing AML, 8 (47.06%) patients developed abnormal karyotypes. High expression of immature myeloid antigens, including CD33 [(49.83 +/- 24.50)%], CD13 [(36.38 +/- 33.84)%], monocytic antigen CD14 [(38.50 +/- 24.60)%], and stem cell marker CD34 [(34.67 +/- 30.59)%], were found on bone marrow mononuclear cells from MDS-AML patients after leukemic transformation. In some cases, lymphoid antigens, such as CD5, CD7, CD9, and CD19, coexisted with myeloid antigens. A low complete remission rate (31.25%) and a short survival time, with median survival of 6 (1 - 28) months, were found in patients with MDS-AML treated by induction chemotherapy. CONCLUSIONS: MDS has a high risk of developing into AML, either gradually or rapidly. Patients with MDS-AML have specific biological characteristics and a worse prognosis.

Endogenous erythroid colony assay in patients with polycythemia vera and its clinical significance.

BACKGROUND: Polycythemia vera (PV) is a malignant disorder of hemaopoietic stem cells which is characterized by clonal hyperproliferation and a low rate of apoptosis. This study was to assess endogenous erythroid colony (EEC) formation in the bone marrow of PV patients and determine its clinical significance. METHODS: The bone marrow mononuclear cells of 26 patients with PV, 2 patients with secondary erythrocytosis (SE), and 19 normal controls were cultured by Marsh's method for EEC evaluation, and the clinical significance was evaluated. RESULTS: EECs appeared in 25 patients with PV but not in 2 patients with SE and 19 normal controls. The number of EECs and the EEC ratio [EEC/erythropoietin (EPO)-dependent colony forming unit-erythroid (CFU-E)] in PV patients positively correlated with hemoglobin (Hb) levels. Their EEC number did not correlate with white blood cell (WBC) counts, platelet (PLT) counts, or leukocyte alkaline phosphatase (LAP) scores. Their EEC did not correlate with serum EPO levels. Fifteen patients with PV were treated with hydroxyurea (Hu) and/or interferon-alpha (IFN-alpha). Their EEC ratio before treatment positively correlated with the treatment time required for complete remission (CR) and negatively correlated with the time before relapse. The EEC numbers of 7 PV patients treated with Hu/IFN-alpha decreased after the blood cell counts dropped to normal levels. There was a positive correlation between the EEC ratio and the incidence of attacks of vascular thrombosis in PV patients. The numbers of apoptosised bone marrow mononuclear cells in PV patients were lower than those in normal controls. The EEC numbers of PV patients negatively correlated with the rate of apoptosis of bone marrow mononuclear cells. CONCLUSIONS: EEC formation is characteristic in PV patients. EEC number in PV patients positively correlates with Hb levels, the time required for CR, and the incidence of attacks of vascular thrombosis. EEC number negatively correlates with the time before relapse. Bone marrow suppressive treatment might decrease EEC number. Thus, EEC number is a sensitive and specific parameter reflecting the abnormal hematopoietic clone burden induced by polycythemia vera. EEC number is an important diagnostic parameter for PV patients.