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Prognostic impact of non-MPN driver gene mutations in primary myelofibrosis. MIPSS70: Mutation-Enhanced International Prognostic Score System.
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Mielofibrose Primária , Humanos , Prognóstico , Mielofibrose Primária/diagnóstico , Mielofibrose Primária/genética , Mutação , Janus Quinase 2/genética , Frequência do GeneRESUMO
Available data have proved insufficient to develop consensus recommendations on the prevention of thrombosis and bleeding in myelofibrosis (MF). We evaluated the incidence and risk factors of vascular complications in 1613 patients from the Spanish Myelofibrosis Registry. Over a total of 6981 patient-years at risk, 6.4% of the study population had at least one thrombotic event after MF diagnosis, amounting to an incidence rate of 1.65 per 100 patient-years. Prior history of thrombosis, the JAK2 mutation, and the intermediate-2/high-risk International Prognostic Scoring System (IPSS) categories conferred an increased thrombotic risk after adjustment for the risk-modifying effect of anti-thrombotic and cytoreductive treatments. History of thrombosis and the JAK2 mutation allowed us to pinpoint a group of patients at higher risk of early thrombosis. No decreased incidence of thrombosis was observed while patients were on anti-thrombotic or cytoreductive treatment. An increased risk of venous thrombosis was found during treatment with immunomodulatory agents. A total of 5.3% of patients had at least one episode of major bleeding, resulting in an incidence rate of 1.5 events per 100 patient-years. Patients in the intermediate-2/high-risk IPSS categories treated with anti-coagulants had an almost sevenfold increased risk of major bleeding. These findings should prove useful for guiding decision-making in clinical practice.
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Mielofibrose Primária , Trombocitemia Essencial , Trombose , Humanos , Mielofibrose Primária/complicações , Mielofibrose Primária/tratamento farmacológico , Mielofibrose Primária/genética , Trombocitemia Essencial/genética , Trombose/epidemiologia , Trombose/etiologia , Trombose/diagnóstico , Hemorragia/diagnóstico , Sistema de Registros , Fatores de RiscoRESUMO
Accurate prognostic tools are crucial to assess the risk/benefit ratio of allogeneic hematopoietic cell transplantation (allo-HCT) in patients with myelofibrosis (MF). We aimed to evaluate the performance of the Myelofibrosis Transplant Scoring System (MTSS) and identify risk factors for survival in a multicenter series of 197 patients with MF undergoing allo-HCT. After a median follow-up of 3.1 years, 47% of patients had died, and the estimated 5-year survival rate was 51%. Projected 5-year risk of nonrelapse mortality and relapse incidence was 30% and 20%, respectively. Factors independently associated with increased mortality were a hematopoietic cell transplantation-specific comorbidity index (HCT-CI) ≥3 and receiving a graft from an HLA-mismatched unrelated donor or cord blood, whereas post-transplant cyclophosphamide (PT-Cy) was associated with improved survival. Donor type was the only parameter included in the MTSS model with independent prognostic value for survival. According to the MTSS, 3-year survival was 62%, 66%, 37%, and 17% for low-, intermediate-, high-, and very high-risk groups, respectively. By pooling together the low- and intermediate-risk groups, as well as the high- and very high-risk groups, we pinpointed 2 categories: standard risk and high risk (25% of the series). Three-year survival was 62% in standard-risk and 25% in high-risk categories (P < .001). We derived a risk score based on the 3 independent risk factors for survival in our series (donor type, HCT-CI, and PT-Cy). The corresponding 5-year survival for the low-, intermediate-, and high-risk categories was 79%, 55%, and 32%, respectively (P < .001). In conclusion, the MTSS model failed to clearly delineate 4 prognostic groups in our series but may still be useful to identify a subset of patients with poor outcome. We provide a simple prognostic scoring system for risk/benefit considerations before transplantation in patients with MF.
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Transplante de Células-Tronco Hematopoéticas , Mielofibrose Primária , Humanos , Mielofibrose Primária/terapia , Prognóstico , Condicionamento Pré-Transplante , Transplante Homólogo , Resultado do TratamentoRESUMO
BACKGROUND: Bone marrow (BM) produces hematopoietic and progenitor cells that contribute to distant organ inflammation and repair. Chronic obstructive pulmonary disease (COPD) is characterized by defective lung repair. Yet, BM composition has not been previously characterized in COPD patients. METHODS: In this prospective and controlled study, BM was obtained by sternum fine-needle aspiration in 35 COPD patients and 25 healthy controls (10 smokers and 15 never-smokers). BM cell count and immunophenotype were determined by microscopy and flow cytometry, respectively. Circulating inflammatory (C-reactive protein, IL-6, IL-8) and repair markers (HGF, IGF, TGF-ß, VEGF) were quantified by ELISA. Results were integrated by multi-level network correlation analysis. RESULTS: We found that: (1) there were no major significant pair wise differences between COPD patients and controls in the BM structural characteristics; (2) multi-level network analysis including patients and controls identifies a relation between immunity, repair and lung function not previously described, that remains in the COPD network but is absent in controls; and (3) this novel network identifies eosinophils as a potential mediator relating immunity and repair, particularly in patients with emphysema. CONCLUSIONS: Overall, these results suggest that BM is activated in COPD with impaired repair capacity in patients with more emphysema and/or higher circulating eosinophils.
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Medula Óssea/imunologia , Medula Óssea/metabolismo , Pulmão/imunologia , Pulmão/metabolismo , Doença Pulmonar Obstrutiva Crônica/imunologia , Doença Pulmonar Obstrutiva Crônica/metabolismo , Idoso , Idoso de 80 Anos ou mais , Medula Óssea/patologia , Células da Medula Óssea/imunologia , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Estudos de Coortes , Feminino , Humanos , Pulmão/patologia , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Mapas de Interação de Proteínas/fisiologia , Doença Pulmonar Obstrutiva Crônica/patologia , Fumar/imunologia , Fumar/metabolismo , Fumar/patologiaRESUMO
Prognostic models are widely used in clinical practice for transplant decision-making in myelofibrosis (MF). We have compared the performance of the International Prognostic Scoring System (IPSS), dynamic IPSS (DIPSS), and DIPSS-plus in a series of 544 patients with primary or secondary MF aged ≤ 70 years at the time of diagnosis. The median projected survival of the overall series was 9.46 years (95% confidence interval 7.44-10.59). Median survival for the highest risk groups was less than 4 years in the three prognostic models. By contrast, the projected survival for patients in the intermediate-2 categories by the IPSS, DIPSS, and DIPSS-plus was 6.6, 5.6, and 6.5 years, respectively. The number of patients in the intermediate-2 and high-risk categories was smaller in the DIPSS than in the IPSS or the DIPSS-plus. The IPSS and DIPSS-plus were the best models to discriminate between the intermediate-1 and intermediate-2 risk categories, which is a critical cut-off point for patient selection to transplant. Among patients assigned at diagnosis to the intermediate-2 or high-risk groups by the IPSS, DIPSS, and DIPSS-plus, only 17, 21, and 20%, respectively, were subsequently transplanted. In conclusion, in our contemporary series of younger MF patients only the highest risk categories of the current prognostication systems have a median survival below the 5-year threshold recommended for considering transplantation. Patient selection for transplantation can significantly differ depending on which prognostication model is used for disease risk stratification.
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Tomada de Decisão Clínica/métodos , Mielofibrose Primária/diagnóstico , Mielofibrose Primária/terapia , Transplante de Células-Tronco/métodos , Idoso , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Mielofibrose Primária/epidemiologia , Prognóstico , Sistema de Registros , Fatores de Risco , Espanha/epidemiologia , Transplante Homólogo/métodosRESUMO
Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera. In patients receiving hydroxyurea, this target can be achieved with hydroxyurea alone or with the combination of hydroxyurea plus phlebotomies. However, the clinical implications of phlebotomy requirement under hydroxyurea therapy are unknown. The aim of this study was to evaluate the need for additional phlebotomies during the first five years of hydroxyurea therapy in 533 patients with polycythemia vera. Patients requiring 3 or more phlebotomies per year (n=85, 16%) showed a worse hematocrit control than those requiring 2 or less phlebotomies per year (n=448, 84%). There were no significant differences between the two study groups regarding leukocyte and platelet counts. Patients requiring 3 or more phlebotomies per year received significantly higher doses of hydroxyurea than the remaining patients. A significant higher rate of thrombosis was found in patients treated with hydroxyurea plus 3 or more phlebotomies per year compared to hydroxyurea with 0-2 phlebotomies per year (20.5% vs. 5.3% at 3 years; P<0.0001). In multivariate analysis, independent risk factors for thrombosis were phlebotomy dependency (HR: 3.3, 95%CI: 1.5-6.9; P=0.002) and thrombosis at diagnosis (HR: 4.7, 95%CI: 2.3-9.8; P<0.0001). The proportion of patients fulfilling the European LeukemiaNet criteria of resistance/intolerance to hydroxyurea was significantly higher in the group requiring 3 or more phlebotomies per year (18.7% vs. 7.1%; P=0.001) mainly due to extrahematologic toxicity. In conclusion, phlebotomy requirement under hydroxyurea therapy identifies a subset of patients with increased proliferation of polycythemia vera and higher risk of thrombosis.
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Hidroxiureia/uso terapêutico , Flebotomia , Policitemia Vera/complicações , Policitemia Vera/terapia , Trombose/epidemiologia , Trombose/etiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Contagem de Células Sanguíneas , Terapia Combinada , Resistência a Medicamentos , Feminino , Hematócrito , Humanos , Hidroxiureia/administração & dosagem , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Fenótipo , Policitemia Vera/diagnóstico , Sistema de Registros , Risco , Espanha/epidemiologia , Trombose/diagnóstico , Fatores de Tempo , Resultado do Tratamento , Adulto JovemRESUMO
OBJECTIVE: Erythropoiesis-stimulating agents (ESAs) are commonly used to treat the anemia of myelofibrosis (MF), but information on the predictors of response is limited. METHODS: Results of ESA therapy were analyzed in 163 MF patients with severe anemia, most of whom had inadequate erythropoietin (EPO) levels (<125 U/L) at treatment start. RESULTS: According to the revised criteria of the International Working Group for Myelofibrosis Treatment and Research, anemia response was achieved in 86 patients (53%). Median response duration was 19.3 months. In multivariate analysis, baseline factors associated with a higher response rate were female sex (P=.007), leukocyte count ≥10×109 /L (P=.033), and serum ferritin <200 ng/mL (P=.002). Patients with 2 or 3 of the above features had a significantly higher response rate than the remainder (73% vs 28%, respectively; P<.001). Over the 373 patient-years of follow-up on ESA treatment, nine patients developed thrombotic complications (six arterial, three venous), accounting for 2.41 events per 100 patient-years. Survival time from ESA start was longer in anemia responders than in non-responders (P=.011). CONCLUSION: Besides the already established predictive value of EPO levels, these data can help to identify which MF patients are more likely to benefit from ESA treatment.
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Anemia , Hematínicos/administração & dosagem , Mielofibrose Primária , Idoso , Anemia/sangue , Anemia/tratamento farmacológico , Anemia/mortalidade , Intervalo Livre de Doença , Eritropoetina/sangue , Feminino , Ferritinas/sangue , Hematínicos/efeitos adversos , Humanos , Contagem de Leucócitos , Masculino , Pessoa de Meia-Idade , Mielofibrose Primária/sangue , Mielofibrose Primária/tratamento farmacológico , Mielofibrose Primária/mortalidade , Fatores Sexuais , Espanha/epidemiologia , Taxa de Sobrevida , Trombose/sangue , Trombose/induzido quimicamente , Trombose/mortalidadeAssuntos
Transplante de Células-Tronco Hematopoéticas/métodos , Síndromes Mielodisplásicas/genética , Síndromes Mielodisplásicas/terapia , TYK2 Quinase/genética , Condicionamento Pré-Transplante/métodos , Adulto , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , Masculino , Polimorfismo Genético , Transplante HomólogoRESUMO
Introduction: NETosis, the mechanism by which neutrophils release extracellular traps (NETs), is closely related to inflammation. During the allogeneic hematopoietic stem cell transplantation (allo-HSCT), different stimuli can induce NETs formation. Inflammation and endothelial injury have been associated with acute graft-versus-host disease (aGVHD) and complications after allo-HSCT. We focus on the study of NETosis and its relation with cytokines, hematological and biochemical parameters and clinical outcomes before, during and after allo-HSCT. Methods: We evaluate the capacity of plasma samples from allo-HSCT patients to induce NETosis, in a cell culture model. Plasma samples from patients undergoing allo-HSCT had a stronger higher NETs induction capacity (NETsIC) than plasma from healthy donors throughout the transplantation process. An optimal cut-off value by ROC analysis was established to discriminate between patients whose plasma triggered NETosis (NETs+IC group) and those who did not (NETs-IC group). Results: Prior to conditioning treatment, the capacity of plasma samples to trigger NETosis was significantly correlated with the Endothelial Activation and Stress Index (EASIX) score. At day 5 after transplant, patients with a positive NETsIC had higher interleukin (IL)-6 and C-reactive protein (CRP) levels and also a higher Modified EASIX score (M-EASIX) than patients with a negative NETsIC. EASIX and M-EASIX scores seek to determine inflammation and endothelium damage, therefore it could indicate a heightened immune response and inflammation in the group of patients with a positive NETsIC. Cytokine levels, specifically IL-8 and IL-6, significantly increased after allo-HSCT with peak levels reached on day 10 after graft infusion. Only, IL-10 and IL-6 levels were significantly higher in patients with a positive NETsIC. In our small cohort, higher IL-6 and IL-8 levels were related to early severe complications (before day 15 after transplant). Discussion: Although early complications were not related to NETosis by itself, NETosis could predict overall non-specific but clinically significant complications during the full patient admission. In summary, NETosis can be directly induced by plasma from allo-HSCT patients and NETsIC was associated with clinical indicators of disease severity, cytokines levels and inflammatory markers.
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Transplante de Células-Tronco Hematopoéticas , Interleucina-6 , Humanos , Interleucina-8 , Citocinas , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , InflamaçãoAssuntos
Mielofibrose Primária , Sistema de Registros , Trombocitopenia , Idoso , Intervalo Livre de Doença , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mielofibrose Primária/sangue , Mielofibrose Primária/diagnóstico , Mielofibrose Primária/mortalidade , Mielofibrose Primária/terapia , Espanha/epidemiologia , Taxa de Sobrevida , Trombocitopenia/sangue , Trombocitopenia/diagnóstico , Trombocitopenia/mortalidade , Trombocitopenia/terapiaRESUMO
Acute myeloid leukemia has a poor prognosis in older adults, and its management is often unclear due to its underrepresentation in clinical trials. Both overall survival (OS) and health-related quality-of-life (HRQoL) are key outcomes in this population, and patient-reported outcomes may contribute to patient stratification and treatment assignment. This prospective study included 138 consecutive patients treated in daily practice with the currently available non-targeted therapies (intensive chemotherapy [IC], attenuated chemotherapy [AC], hypomethylating agents [HMA], or palliative care [PC]). We evaluated patients' condition at diagnosis (Life expectancy [Lee Index for Older Adults], Geriatric Assessment in Hematology [GAH scale], HRQoL [EQ-5D-5L questionnaire], and fatigue [fatigue items of the QLQ-C30 scale]), OS, early death (ED), treatment tolerability (TT) and change in HRQoL over 12 months follow-up. The median OS was 7.1 months (IC not reached, AC 5.9, HMA 8.8, and PC 1.0). Poor risk AML category and receiving just palliative care, as well as a higher Lee index score in the patients receiving active therapy, independently predicted a shorter OS. The Lee Index and GAH scale were not useful for predicting TT. The white blood cell count was a valid predictor for ED. Patients' HRQoL remained stable during follow-up.
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Background: The lysis of platelets during in vitro coagulation leads to increased potassium concentrations.We aimed to establish the cut-off value for platelet count interfering serum potassium and to estimate the percentage of cases of pseudohyperkalemia and pseudonormokalemia in our hospital. Materials and methods: Individuals diagnosed with essential thrombocytosis (2010-2019) based on the WHO criteria for the classification of myeloid neoplasms and acute leukemia were considered.The cut-off value for the interference of platelet count on serum potassium results was calculated using the reference change value. Sensitivity and specificity were calculated using a ROC-curve, and the size of the effect by the Cohen's d.The clinical impact of both phenomena was assessed by reviewing the medical records of individuals classified as such, and also looking for potential cases in 2019 on the laboratory information system. Results: Fifty-four individuals with essential thrombocytosis were included. Potassium concentration correlated with platelet count (P-value<0.001; Spearman's ρ =0.394) in serum. The cut-off value of platelet count interfering potassium was 598x103/µL [CI95%: 533-662x103/µL], with an associated sensitivity and specificity of 0.67 [CI95%:0.52-0.80] and 0.58 [CI95%:0.42-0.72] respectively.The medical records of patients classified as pseudohyperkalemia or pseudonormokalemia did not include any medical action for the modification of potassium levels. In 2019, up to 0.14% of the total serum potassium determinations were susceptible to be pseudohyperkalemia or pseudonormokalemia. Conclusion: This study provides a cut-off value for platelet count interfering serum potassium concentrations, and brings to light not only pseudohyperkalemia-related issues, but also the pseudonormokalemia phenomenon, which usually goes unnoticed.
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Primary familial and congenital polycythemia is a rare disease characterized by an increase in red cell mass that may be due to pathogenic variants in the EPO receptor (EPOR) gene. To date, 33 genetic variants have been reported to be associated. We analyzed the presence of EPOR variants in two patients with polycythemia in whom JAK2 pathogenic variants had been previously discarded. Molecular analysis of the EPOR gene was performed by Sanger sequencing of the coding regions and exon/intron boundaries of exon 8. We performed in vitro culture of erythroid progenitor cells. Segregation studies were done whenever possible. The two patients studied showed hypersensitivity to EPO in in vitro cultures. Analysis of the EPOR gene unveiled two novel pathogenic variants. Genetic testing of asymptomatic relatives could guarantee surveillance and proper management.
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Policitemia , Receptores da Eritropoetina , Humanos , Receptores da Eritropoetina/genética , Policitemia/genética , Policitemia/congênito , Policitemia/patologiaRESUMO
Cytogenetic studies have played a crucial role in the discovery of genes involved in several diseases. In the field of oncohematology, cytogenetics is still necessary for the classification and prognosis of many diseases. Here we report a new recurrent chromosome translocation, t(10;12)(q24;q15), in two patients with different hematological malignancies: myelodysplastic syndrome with excess blasts (MDS-EB), and myelofibrosis (MF) secondary to essential thrombocythemia (ET). The chromosome alteration was observed as a sole karyotype change in the patient with MDS-EB, both at the initial diagnosis and following progression to MDS-EB2. A putative HMGA2-KLLN rearrangement by RNA-sequencing was detected in this patient. The patient with ET, had a normal karyotype at diagnosis and the t(10;12)(q24;q15) translocation emerged as a sole cytogenetic alteration after transformation, and when MF was evident. We reviewed the literature to determine whether this chromosome abnormality had previously been described in other hematological patients and found two cases: an aggressive T-cell lymphoblastic lymphoma (T-LBL) and a case of transformed chronic myeloproliferative syndrome (CMS), in both of which t(10;12)(q24;q15) was also the only karyotype change. The clinical evolution of all four cases suggested that t(10;12)(q24;q15) is associated with a poor outcome in oncohematological patients.
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Neoplasias Hematológicas , Síndromes Mielodisplásicas , Trombocitemia Essencial , Aberrações Cromossômicas , Análise Citogenética , Citogenética , Neoplasias Hematológicas/genética , Humanos , Síndromes Mielodisplásicas/genética , Síndromes Mielodisplásicas/patologia , Trombocitemia Essencial/genética , Translocação GenéticaRESUMO
BACKGROUND AND OBJECTIVE MYELOFIBROSIS: is an infrequent chronic myeloproliferative neoplasm. We aimed to describe the clinico-biological characteristics, treatment, and evolutive course of myelofibrosis patients in Spain. MATERIAL AND METHODS: A total of 1,000 patients from the Spanish Registry of Myelofibrosis diagnosed with primary (n=641) or secondary (n=359) myelofibrosis were analysed. RESULTS: Median age was 68 years. The frequency of constitutional symptoms, moderate to severe anaemia (Hb<10g/dL), and symptomatic splenomegaly was 35%, 36%, and 17%, respectively. The rate of thrombosis and haemorrhage was 1.96 and 1.6 events per 100 patient-years, respectively. The cumulative incidence of leukaemia at 10 years was 15%. The most frequent therapies for the anaemia were the erythropoiesis stimulating agents and danazol. From 2010, a progressive increase in the use of ruxolitinib was noticed. A total of 7.5% of patients were transplanted. During the observation period, 42% of patients died mainly due to the clinical deterioration caused by myelofibrosis or leukaemic transformation. The median survival of the series was 5.7 years. Four different risk categories were identified by the IPSS: median survival was not reached in the low risk group and was 8.8 years, 5.3 years, and 2.8 years in the intermediate-1, intermediate-2, and high-risk groups, respectively. CONCLUSIONS: Myelofibrosis is a disabling condition mainly affecting elderly people. Its treatment is mostly driven by symptom control. Despite its clinical heterogeneity, several prognostic models are useful to select candidates for transplantation.
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Mielofibrose Primária , Idoso , Humanos , Mielofibrose Primária/diagnóstico , Mielofibrose Primária/epidemiologia , Prognóstico , Sistema de Registros , Espanha/epidemiologia , EsplenomegaliaRESUMO
Bone marrow infiltration by alveolar rhabdomyosarcoma is uncommon, some cases can mimicry acute leukemia at presentation and mislead the diagnosis. The integration of diagnostics tests and techniques in uncommon malignancies is important to suspect and reach the diagnosis and avoid delay on treatment. We report a case of alveolar rhabdomyosarcoma bone marrow infiltration associated with hemophagocytosis and cell cannibalism, mimicking acute leukemia at presentation.
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Duplication of the long arm of chromosome 1 (1q) has been detected accompanied with other chromosome abnormalities in Myelodysplastic Syndromes (MDS). However, as a sole karyotypic change, it is rarely observed. We present here two patients affected of a MDS that showed a dup(1)(q21q32) as a sole cytogenetic change in their bone marrow cells. Complementary methodologies confirmed the duplication of chromosome 1q and, did not show additional cryptic chromosome abnormalities. One patient acquired a secondary trisomy 8 and the other one progressed toward an acute leukemia with no additional cytogenetic alterations.
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Aberrações Cromossômicas , Cromossomos Humanos Par 1 , Leucemia/genética , Síndromes Mielodisplásicas/genética , Bandeamento Cromossômico , Cromossomos Humanos Par 8 , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Cariotipagem Espectral , TrissomiaRESUMO
AIM: To characterise the clinical and histological features of MPL-mutated essential thrombocythaemia (ET). PATIENTS AND METHODS: Bone marrow biopsies of 175 patients with ET were centrally reviewed according to the 2016 WHO classification, including 42 cases with MPL mutation, 98 JAK2V617F-mutated and 35 CALR-mutated. Clinical and histological features were compared among the three genotypes included in the current 2016 WHO classification and among the different types of MPL mutations. RESULTS: Patients with MPL-mutated ET were significantly older than those with the other genotypes. Haematological values at diagnosis were similar among MPL-mutated and CALR-mutated ET, with both genotypes showing higher platelet counts and lower haemoglobin values than ET with JAK2V617F genotype. In the bone marrow, the median number of megakaryocytes was higher in MPL and CALR than in JAK2V617F genotype (16, 19 and 14 megakaryocytes per ×20 power field, respectively, p=0.004). Histological features of prefibrotic myelofibrosis were rarely observed in MPL genotype, whereas sinusoidal hyperplasia, dense clusters of megakaryocytes and reticulin fibrosis were more frequent in CALR-mutated ET, with 11% of such cases fulfilling WHO 2016 histological criteria of prefibrotic myelofibrosis. With a median follow-up of 3.5 years, no significant differences were seen among genotypes regarding survival, vascular complications or myelofibrotic transformation. There were no significant differences in the clinical data or in the histological characteristics depending on the type of MPL mutation. CONCLUSION: MPL and CALR ET genotypes share clinical and histological characteristics. In contrast to CALR genotype, features of prefibrotic myelofibrosis are uncommon in MPL-mutated ET.