Treatment with low-dose, single-agent belantamab mafodotin is safe and provides long-term responses in heavily pretreated multiple myeloma patients.

OBJECTIVES: To evaluate whether low-dose belantamab mafodotin (B-MAF) dosing results in lower toxicity and better overall outcome. METHODS: We retrospectively evaluated nine consecutive patients treated with low-dose (1.9 mg/kg) B-MAF. RESULTS: The median age was 70 years. Most patients were penta-refractory. Ocular toxicity was observed in 77.7%. Adverse events resulting in treatment delays were recorded in 9 out of 124 cycles being given. Overall response rate was 66% (6/9), and all responding patients achieved very good partial response or better. Within a median follow-up of 12 (range 0.5-13.8) months, median progression-free survival and overall survival were 14 (CI95% 6-22) and 20 (95%CI 0-41) months, respectively. CONCLUSION: Low-dose B-MAF regimen showed high-efficacy and low-toxicity profile.

Real-world experience with belantamab mafodotin therapy for relapsed/refractory multiple myeloma: A multicentre retrospective study.

Belantamab mafodotin, an immuno-conjugate targeting B-cell maturation antigen, showed single-agent activity in phase 1 and 2 studies, and was recently approved for heavily pretreated relapsed/refractory multiple myeloma (RRMM) patients. Real-world data and long-term follow-up are scarce. We conducted a multisite retrospective study aimed to assess safety and efficacy of belantamab mafodotin monotherapy administered via the GSK expanded access compassionate care programme. One-hundred and six RRMM patients were treated with belantamab mafodotin between July 2019 and March 2021. The median age was 69.4 years. Patients were heavily pretreated with a median of six (range 2-11) prior therapy lines. Major adverse effects included ocular toxicity (keratopathy 68.4%, grade ≥3: 40.5%; blurred vision 36.8%, grade ≥3: 6.3%), thrombocytopenia (27.4%, grade ≥3: 17.9%) and infections (11.3%, grade ≥3: 7.5%). Median follow-up time was 11.9 [95% confidence interval (CI) 10.0-13.8] months. Overall response rate was 45.5%. Median progression-free survival was 4.7 (95% CI 3.5-5.9) months in the entire cohort and 8.8 (95% CI 6.6-10.9) months among responders. Median overall survival was 14.5 (95% CI 9.5-19.6) months, and not reached for responders. To conclude, in a real-world setting, belantamab mafodotin monotherapy showed efficacy comparable with the prospective clinical trials, with a tolerable toxicity profile.

Clinical features, therapy patterns, outcomes and prognostic factors of solitary plasmacytomas: a report of the Israeli Myeloma Study Group.

Solitary plasmacytoma (SP) is a rare plasma cell dyscrasia. In this retrospective multicenter study, 68 SP patients were included. Compared to solitary extramedullary plasmacytoma (SEP), patients with solitary bone plasmacytoma (SBP) were younger (57.3 vs. 70.9 years, p = 0.031), had larger plasmacytoma (median: 5.4 vs. 3 cm, p = 0.007) and higher median involved free light chain level (61 vs. 25.8 mg/L, p = 0.056). 92.6% of patients were treated by radiotherapy and 11.8% received systemic anti-myeloma treatment. With a median follow-up of 42 months, 45.6% of patients progressed (8.8% - recurrent SP, 36.8% - active myeloma). The median PFS was 58 months and the median OS has not been reached (10-year OS: 84.8%). Patients who received also anti-myeloma treatment had longer PFS compared to those who did not (median not reached vs. 48 months, p = 0.056). In conclusion, SBP and SEP appear to be different diseases. Radiotherapy is the cornerstone in the SP treatment. A large prospective trial is needed to evaluate the impact of adding systemic anti-myeloma treatment to local radiotherapy.

Daratumumab in combination with proteasome inhibitors, rapidly decreases polyclonal immunoglobulins and increases infection risk among relapsed multiple myeloma patients: a single center retrospective study.

BACKGROUND: Daratumumab (Dara) is generally well tolerated, but is associated with increased risk of infection. METHODS: We investigated hypogammaglobinemia occurrence in different Dara-based regimens. Multiple myeloma (MM) patients were treated with ⩾2 cycles of Dara-based therapy during 2016-2020, mainly for relapsed/refractory disease. Data on patient characteristics, treatment regimens, polyclonal IgG (poly-IgG) and uninvolved free light chain (Un-FLC) levels during treatment, as well as predictors for hypogammaglobinemia and predictors for infections, were evaluated retrospectively. RESULTS: A total of 84 patients, median age 67.2 years, were included. Dara, mainly as ⩾2 line therapy (88.1%, n = 74), was combined with immunomodulating drugs (IMiDs) (53%), proteasome inhibitors (PIs) (15%), IMiDs-PIs (11%), or dexamethasone only (21%). Median treatment duration was 13 months. Median Poly-IgG levels at 0, 2, and 4 months were 7.1 g/l, 4.5 g/l, and 4 g/l, respectively, and remained low throughout treatment. Lower poly-IgG pre-Dara (p = 0.001) and Dara-PIs (±IMiDs) regimen were associated with lower poly-IgG levels at 4 months (p = 0.03). Only patients treated with Dara monotherapy had partial immune reconstitution, reflected by resumption of IgM levels. Most (85%) patients developed ⩾1 infections, mostly grade 1-2 respiratory (76%). A lower poly-IgG level post Dara (RR = 1.137 p = 0.026) predicted increased risk of any infection. Intravenous immunoglobulin (IVIG) was associated with a significant decrease in all infections. CONCLUSION: Relapsed MM patients treated with Dara, often experience persistent hypogammaglobinemia, irrespective of responsiveness to treatment. Infections, especially respiratory, are frequent and apparently related to low Poly-IgG levels. IVIG should be considered for reducing infections in these patients.

Humoral response rate and predictors of response to BNT162b2 mRNA COVID19 vaccine in patients with multiple myeloma.

Multiple myeloma (MM) patients are at excess risk for clinically significant COVID19 infection. BNT162b2 mRNA COVID19 (BNT162b2) vaccine provides effective protection against COVID19 for the general population, yet its effect in MM patients may be compromised due to disease and therapy-related factors and was not yet evaluated. This single-centre prospective study included MM patients tested for serological response 14-21 days post second vaccine. Vaccinated healthy volunteers served as controls. In all, 171 MM patients, median age 70 (38-94) were included; 159 active MM and 12 smouldering myeloma (SMM). Seropositive response rate (median titer) was 76% (91 U/ml) in active MM patients vs 98% (992 U/ml) in the 64 controls (P < 0·0001), and 100% (822 U/ml) in SMM patients. Multivariate analysis revealed older age (P = 0·009), exposure to ≥4 novel anti-myeloma drugs (P = 0·02) and hypogammaglobulinaemia (P = 0·002) were associated with lower response rates. None of the novel agents significantly decreased response rate, whereas daratumumab trended towards reduced response (P = 0·08). Adverse events occurred in 53% and 55% of the MM patients and controls, respectively, all transient grade 1-2. In conclusion, BNT162b2 vaccine was safe and provided a high seropositivity rate in MM patients, independent of treatment type. Older, hypogammaglobulinaemic and heavily pretreated patients had lower response rates.

Characteristics and outcome of multiple myeloma patients presenting with anaemia only: A retrospective multi-centre study.

BACKGROUND: Multiple myeloma (MM) patients presenting with anaemia as their sole clinical manifestation are rare and not fully defined. METHODS: Retrospective multi-site study comparing the characteristics and outcome of MM patients with anaemia only with matched patients, presenting with multi-organ disease. RESULTS: Anaemia-only patients had a higher percentage of bone marrow monoclonal plasma cells group (median 60% [IQR 42-80%] vs. 37% [IQR 17-65%], respectively; p < 0.001), and a lower responsiveness to treatment (≥VGPR rates were 54% vs 74%, p = 0.049). Median survival in anaemia only patients was 65.9 ± 6.9 vs 83.4 ± 8.8 months in matched control patients (P = n.s). CONCLUSIONS: MM patients presenting with anaemia only represents a unique, potentially less favorable population.

Bortezomib Maintenance Therapy as a Standard of Care Provides Favorable Outcomes in Newly Diagnosed Myeloma Patients: A Multisite Real-Life Study.

BACKGROUND: Lenalidomide and ixazomib maintenance improve long-term outcomes in newly diagnosed multiple myeloma (NDMM) patients. However, there is less evidence to support bortezomib (BTZ) maintenance therapy, and real-life data on maintenance are scarce. We investigated the efficacy and safety of BTZ maintenance therapy in NDMM. PATIENTS AND METHODS: A retrospective multisite study was performed in 6 medical centers in Israel. All consecutive patients with NDMM diagnosed between January 1, 2010, and July 3, 2019, who received a BTZ-based induction, with or without an autologous transplantation, followed by BTZ maintenance therapy, were identified. Maintenance therapy was defined as BTZ (1.3 mg/m2) once every 2 weeks, administered subcutaneously alone or with dexamethasone, or weekly BTZ monotherapy. RESULTS: A total of 105 patients were identified, 58 of whom had received a transplant (transplant eligible) and 47 who had not (not transplant eligible). During BTZ maintenance therapy, 96% had one or more adverse event, 11.5% had grade 3 or higher adverse events, and 11.5% discontinued treatment due to toxicity. Median progression-free survival (PFS) and overall survival were 45 and 91.5 months, respectively; 4-year survival was 88%. Adverse cytogenetics was associated with worse PFS (24 vs. 46 months, P = .001). In subgroup analysis, adverse cytogenetics were associated with worse PFS (P < .001) and OS (P < .001) among transplant-ineligible but not transplant-eligible patients. CONCLUSION: Analysis of multisite real-life data showed that BTZ maintenance therapy is safe, well tolerated, and effective. Median PFS was similar to that reported with alternative maintenance strategies. Our findings further support its use among patients with adverse cytogenetics, it may also be relevant for patients with lenalidomide-intolerant disease.

Components of metabolic syndrome in patients with multiple myeloma and smoldering multiple myeloma.

BACKGROUND: The prevalences of diabetes mellitus and hypertension, both of which are components of metabolic syndrome, are known to be increased among patients with multiple myeloma (MM), but remain undetermined among patients with smoldering MM (SMM). METHODS: Changes in various components of metabolic syndrome were investigated during the follow-up of patients with either MM or SMM compared to healthy controls. The data of 153 patients (105 with MM and 48 with SMM) and 138 controls were accessed from our medical center's records between 2008 and 2015. We analyzed the patients' data at diagnosis (baseline) and after 1, 3, and 5 years of follow-up. RESULTS: Patients with SMM had a significantly higher prevalence of diabetes, hypertension, and dyslipidemia at baseline compared to controls. A multivariate Cox regression analysis revealed a higher risk to develop dyslipidemia after 1, 3, and 5 years of follow-up among the SMM patients. The MM patients had a higher risk to develop diabetes after 1 year, hypertension after 5 years, and dyslipidemia after 1, 3, and 5 years of follow-up. CONCLUSIONS: These data demonstrate that patients with SMM and those with MM are more prone to develop various components of metabolic syndrome, and they stress the importance of following-up metabolic syndrome components in both groups of patients.

Bortezomib washout duration prior to stem cell mobilization in patients with newly diagnosed multiple myeloma.

OBJECTIVES: We aimed to determine the impact of washout period in patients with multiple myeloma between bortezomib-based induction regimens and the collection of stem cells. METHODS: This was a single-center historical prospective study, including all sequential newly diagnosed patients with myeloma between 2012 and 2017 that were given a first-line bortezomib-based induction therapy (≤6 cycles) followed by stem cell collection (n = 75). RESULTS: We found a statistically significant correlation between the days from last dose of bortezomib and both CD34+ cells/kg yield on the first collection day and the overall collected CD34+ cells/kg (r = .466, P < .001, and r = .341, P = .03, respectively). The optimal receiver operating curve's cutoff point was 8.5 days (79% sensitivity and 71% specificity, P = .001). On multivariate analysis, timing of last dose of bortezomib remained statistically significant (P = .01). Based on this, we developed a model to predict the total collected CD34+ cells/kg = 11.76 + 0.13 (timing in days of last dose of bortezomib) -0.1 (age) -1.39 (if female) -0.01 (≥PR) -1.35 (if prior radiation). CONCLUSIONS: Timing of last dose of bortezomib may predict a successful collection. A washout period of 9 days is associated with a better collection yield. A prospective validation of this novel finding is required.

Ixazomib-based regimens for relapsed/refractory multiple myeloma: are real-world data compatible with clinical trial outcomes? A multi-site Israeli registry study.

Ixazomib, the first oral proteasome inhibitor (PI), has been approved for the treatment of relapsed refractory multiple myeloma (RRMM) in combination with lenalidomide and dexamethasone, based on the TOURMALINE-MM1 phase 3 trial, which demonstrated the efficacy and safety of this all-oral triplet, compared with lenalidomide-dexamethasone. However, clinical trial outcomes do not always translate into real-world outcomes. The aim of this study was to assess the outcomes of ixazomib-based combination for treatment of patients with RRMM in a real-world setting. All consecutive RRMM patients who received at least one cycle of ixazomib-based treatment combination between June 2013 and June 2018 were identified. Data was extracted from medical charts focusing on demographics, disease characteristics, prior treatment, and responses. Primary endpoint was progression-free survival (PFS); secondary endpoints included overall response rate (ORR), overall survival (OS), safety, and tolerability. A total of 78 patients across 7 sites were retrospectively included. Median follow-up was 22 months. Median age was 68 (range 38-90). Sixty-four percent received ixazomib in 2nd line, 19% in 3rd line. Overall, 89% of patients had been exposed to PIs (bortezomib 87%) prior to IRd, 41% to IMiDs. Twenty-nine (48%, of 60 available) had high (t(4:14), t(14:16), del17p) or intermediate (+1q21) risk aberrations. Most patients (82%) received ixazomib in combination with lenalidomide and dexamethasone. An exploratory assessment for disease aggressiveness at diagnosis was classified by a treating physician as indolent (rapid control to protect from target organ damage not required) vs aggressive (imminent target organ damage) in 63% vs 37%, respectively. Treatment was well tolerated, with a low discontinuation rate (11%). Median PFS on ixazomib therapy was 24 months (95% CI 17-30). PFS was 77% and 47% at 12 and 24 months, respectively. Median OS was not reached; OS was 91% and 80% at 12 and 24 months, respectively. Higher LDH, older age, and worse clinical aggressiveness were associated with worse PFS, whereas a deeper response to ixazomib (≥ VGPR) and a longer response to first-line bortezomib (≥ 24 m) were associated with an improved PFS on ixazomib. No effect on PFS was found for cytogenetic risk by FISH, ISS/rISS, and prior anti-myeloma treatment. Ixazomib-based combinations are efficacious and safe regimens in RRMM patients in the real-world setting, regardless to cytogenetic risk, with a PFS of 24 months comparable with clinical trial data. This regimen had most favorable outcomes among patients who remained progression-free more than 24 months after a bortezomib induction and for those who have a more indolent disease phenotype.

Impaired lymphocyte reconstitution after autologous transplant is associated with apoptosis of CD8+ T cells and adverse clinical outcome.

We noticed that the lymphocyte counts, after autologous hematopoietic stem cell transplantation, oscillated during the first 4 post-transplant months. Thereafter, the lymphocyte counts stabilized and segregated the patients into two groups, those who normalized their lymphocyte counts and those with prolonged lymphopenia. In both groups, the CD4 counts remained low for at least 6 months. However, in approximately half of the patient, the CD8 counts increased to normal or above normal values. Patients with prolonged lymphopenia had higher rates of lymphocytes' spontaneous apoptosis and the lymphocytes in patients who restored their counts expressed the intracellular CD14-derived MO2 epitope that protects the cells from apoptosis. These findings were translated to longer disease-free survival and overall survival in patients who restored the CD8 counts. Collectively, our data show that post-transplant lymphocytes that express intracellular CD14-MO2 epitope have survival advantage.

Treatment patterns and clinical outcomes in high-risk newly diagnosed multiple myeloma patients carrying the 17p deletion: An observational multi-center retrospective study.

Del17p is a genomic imbalance occurring in ∼7%-10% of myeloma at diagnosis newly diagnosed myeloma patients (NDMM) and comprises a poor prognostic factor. The goal of this study is to analyze real world data and outcomes among NDMM patients carrying 17p deletion. We report an observational, retrospective, multicenter study. Sixty consecutive patients diagnosed with multiple myeloma in the 8 participating centers diagnosed between 1/2008 and 1/2016 proven to carry 17p deletion by means of fluorescence in situ hybridization (FISH) were identified. Most received a bortezomib-based induction, over half underwent autologous hematopoietic cell transplantation (HCT); 30% of the patients gained early access to new novel agents via clinical trials, access programs or private insurance. Overall response rate (ORR) after induction was 85%; 94% for transplant eligible (TE); and 75% for transplant ineligible (NTE), and declined in subsequent treatment lines, 64% achieved ≥ VGPR. Median overall survival (OS) was 43 months; median progression free survival (PFS) was 11 months, 19 months for TE and 7 for NTE. In multivariate analysis: higher M-Spike, presence of extramedullary disease, and >50% of cells baring del17p were associated with adverse PFS; Autologous HCT and higher hemoglobin were associated with longer PFS; OS was 59 months for patients with early access to newer agents. Older age and higher M-Spike levels were associated with adverse OS, Autologous HCT was associated with favorable OS, 59.7 vs 28.7 months for NTE patients. Despite the improvement achieved with autologous HCT and new novel agents, the prognosis of patients with 17p deletion is still inferior, emphasizing the need for novel approaches.

Efficacy and safety of autologous hematopoietic cell transplantation in elderly patients with multiple myeloma: a retrospective national multi-site cohort study.

We aimed to test the efficacy and toxicity of autologous hematopoietic cell transplant (HCT) in Multiple Myeloma (MM) patients aged ≥65 years compared to patients aged 60-64. Two hundred twenty consecutive patients (age ≥65, n = 87) with MM aged 60 and above, who underwent HCT as part of an upfront MM treatment, at four Israeli centers between 2000 and 2014 were included. A melphalan dose of 200 mg/m2 was more frequent in the 60-64 age group vs. the ≥65 age group (77 vs. 57%, p = 0.002). There were no differences between groups in median day of neutrophil engraftment, incidence of infections, grades 3-4 mucositis, cardiovascular events, or non-relapse mortality at 100 days post HCT (4.7, vs. 5%, p = 0.9). A similar rate of improvement in response level was observed (36, vs. 35%, p = 0.87). At 3 years post HCT progression-free survival (PFS) was higher in the 60-64 age group (42 vs. 29%, p = 0.04); however, it was no longer so after adjustment for disease status prior to HCT (p = 0.49). In a Multivariate analysis, melphalan doses and age did not predict PFS. There was no difference in overall survival (OS) between age groups (p = 0.2). We conclude that toxicity profile, response, PFS, and OS of HCT in aged ≥65 patients with myeloma is similar to patients aged 60-64.

Serum free immunoglobulin light chain fingerprint identifies a subset of newly diagnosed multiple myeloma patients with worse outcome.

Multiple myeloma (MM) is a multi-subclonal malignancy with relatively high heterogeneity. Patients who initially presented with both monoclonal-protein (MP) and free light chain (FLC) secretion but then relapsed with a light chain escape pattern have been shown to reflect disease clonal evolution and to bare a worse prognosis. We hypothesized that a discordant MP/FLC pattern at diagnosis may reflect a similar clonal evolution that had occurred prior to diagnosis of active myeloma, conferring a worse outcome. We analyzed 255 consecutive newly diagnosed MM patients who received first line bortezomib-based therapy between 2007 and 2014, hypothesizing that their MP/FLC fingerprint at diagnosis reflects clonal heterogeneity and, therefore, affects outcome. An involved FLC level ≥ 700 mg/L and MP ≥ 2.5 g/L were used as cutoffs for low vs high FLC and MP levels, respectively. Patients were divided into 4 subgroups according to their involved FLC and MP blood levels at diagnosis: HiLC and HiMP for patients with either a predominant FLC or a predominant MP, respectively, and HiLC-MP and LoLC-MP when both FLC and MP were increased or decreased, respectively. There were 68 (27%) patients with HiLC, which presented more often with International Staging System-3 stage (P < .0001). Multivariate analysis showed that HiLC was associated with a 5.1-fold risk for mortality in a multivariate model (95% confidence interval [CI], 1.34-19.68). Both HiLC and HiLC-MP phenotypes were associated with shorter progression-free survival (hazard ratio of 2.66 [95% CI, 1.33-5.32] and 2.82 [95% CI, 1.37-5.83], respectively), independently of other prognostic factors, including the use of autograft. Thus, we identified an LC predominant secretory fingerprint (HiLC phenotype) at diagnosis as a potential independent risk factor that may affect disease control and survival in newly diagnosed MM patients treated with bortezomib-based induction therapy; this may represent increased subclonal heterogeneity.

Primary failure of bortezomib in newly diagnosed multiple myeloma--understanding the magnitude, predictors, and significance.

Botezomib-based induction is highly effective for the treatment of newly diagnosed multiple myeloma (NDMM). We investigated the outcomes of NDMM patients who failed to respond to bortezomib-based induction in a 'real-life' clinical setting. In a cohort of 295 consecutive NDMM patients in 3 medical centers, 74 (25%) failed to achieve at least partial response after 4 induction cycles, and were classified as non-responsive. Compared to induction responders, they were older, more frequently anemic, had a higher incidence of del17p and ISS-3, and a worse performance status. In multivariable analysis, bortezomib-based induction failure occurred in 25% of patients and was the strongest independent factor predicting mortality with a 5-fold hazard ratio (95% CI 1.44-8.68). Three-year overall survival in responsive vs. non-responsive patients were 76% vs. 53%, respectively (p < 0.0001). Survival from time of salvage second-line treatment was significantly shorter among induction non-responders vs. responders (25 months vs. not-reached, p = 0.024).

Outcomes of light-chain amyloidosis patients treated with first-line bortezomib: a collaborative retrospective multicenter assessment.

Light-chain amyloidosis (AL) is associated with low survival rates, particularly in patients with cardiac involvement. We evaluated the outcome of 73 consecutive, non-selected 'real-world' AL patients, treated with first-line bortezomib-based induction, focusing on the benefit of concurrent administration of alkylating agents. Most patients had renal (77%), cardiac (66%), or multiorgan (74%) involvement. Sixty-eight per cent (n = 50) received alkylating agent (mostly cyclophosphamide). Severe adverse events were seen in 45%, most evident in patients with cardiac involvement, with no increased toxicity in patients receiving an alkylator agent. Hematological response (HemR) was obtained in 77% of patients, including 33% very good partial responses and 19% complete responses. Age <70 yr, lack of cardiac and peripheral neurologic involvement, and co-administration of an alkylating agent were associated with significantly improved HemR. NYHA cardiac failure staging was the only independent factor affecting overall survival. Administration of an alkylating agent and the achievement of both HemR and organ response were associated with a statistically significant improved survival in those surviving the first 6 months of induction. First-line bortezomib-based regimen resulted in favorable response and survival in newly diagnosed patients. Co-administration of an alkylating agent improved outcome without increasing treatment-related toxicity.

Divergence in CD19-mediated signaling unfolds intraclonal diversity in chronic lymphocytic leukemia, which correlates with disease progression.

Emerging data on intraclonal diversity imply that this phenomenon may play a role in the clinical outcome of patients with chronic lymphocytic leukemia (CLL), where subsets of the CLL clone responding more robustly to external stimuli may gain a growth and survival advantage. In this study, we report intraclonal diversity resolved by responses to CD19 engagement in CLL cells, which can be classified into CD19-responsive (CD19-R) and -nonresponive subpopulations. Engagement of CD19 by anti-CD19 Ab rapidly induced cellular aggregation in the CD19-R CLL cells. The CD19-R CLL cells expressed higher surface levels of CD19 and c-myc mRNA, exhibited distinct morphological features, and were preferentially abolished in rituximab-treated patients. Both subpopulations reacted to sIgM stimulation in a similar manner and exhibited similar levels of Akt and Erk phosphorylation, pointing to functional signaling divergence within the BCR. CD19 unresponsiveness was partially reversible, where nonresponding CD19 cells spontaneously recover their signaling capacity following incubation in vitro, pointing to possible in vivo CD19-signaling attenuating mechanisms. This concept was supported by the lower CD19-R occurrence in bone marrow-derived samples compared with cells derived from the peripheral blood of the same patients. CLL patients with >15.25% of the CD19-R cell fraction had a shorter median time to treatment compared with patients with <15.25% of CD19-R cell fraction. In conclusion, divergence in CD19-mediated signaling unfolds both interpatient and intraclonal diversity in CLL. This signaling diversity is associated with physiological implications, including the location of the cells, their responses to anti-CLL therapeutics, and disease progression.

JAK2 mutation: an aid in the diagnosis of occult myeloproliferative neoplasms in patients with major intraabdominal vein thrombosis and normal blood counts.

BACKGROUND: Janus kinase-2 (JAK2) is mutated in a high proportion of patients with polycythemia vera and in a smaller number with essential thrombocythemia and primary myelofibrosis. Mutated JAK2 is an important diagnostic marker for myeloproliferative neoplasm (MPN) and may also play a major role in the pathogenesis of MPN. OBJECTIVES: To evaluate the prevalence of mutated JAK2 (JAK2-V617F) among patients with major intraabdominal vein thrombosis who had normal blood counts at diagnosis of the initial event. METHODS: The medical records of patients who presented with a major intraabdominal venous thrombosis and normal peripheral blood counts were obtained. JAK2-V617F mutation status was determined by real-time polymerase chain reaction. RESULTS: Twenty-two patients were available for this analysis and 9 (41%) were found to have JAK2-V617F. Patients with positive JAK2-V617F were younger and had more frequent clinical splenomegaly than those with wild-type JAK2. CONCLUSIONS: A high proportion of patients presenting with "idiopathic" major intraabdominal vein thrombosis and normal blood counts carry JAK2-V617F. We recommend searching for the mutation in this clinical setting to detect patients with occult MPN.