Prevalence of the JAK2 V617F mutation associated with splanchnic vein thrombosis. A 10-year retrospective study

JAK2 (V617F) Positive Latent Myeloproliferative Neoplasm Presenting with Splanchnic Vein Thrombosis

Myeloproliferative neoplasms (MPNs) are chronic clonal hematopoietic stem cell disorders characterized by proliferation of one or more of the granulocytic, red cell or platelet lineages in the bone marrow, with fairly normal maturation, resulting in increase in the leukocyte, erythrocytes and platelets in the blood. They also represent a common cause of splanchnic vein thrombosis (SVT). Herein, we describe a case of SVT as a presenting symptom of latent MPN. The patient has had normal complete blood counts since presentation. 3 ½ years later, she was found to have JAK2 (V617F) mutation and bone marrow biopsy was consistent with MPN. Five years later, her platelet count started to rise. In patients with a first episode of SVT, thrombophilia workup including JAK2 (V617F) mutation is warranted. Anticoagulation with heparin and warfarin is the treatment of choice for SVT.

Thrombotic complications of myeloproliferative neoplasms: risk assessment and risk-guided management

Philadelphia-negative myeloproliferative neoplasms are considered to be acquired thrombophilic states. Thromboses, both arterial and venous (not rarely in unusual sites), are often the initial events leading to the diagnosis. After diagnosis, the yearly incidence of thrombotic events is highly variable, and ranges from approximately 1% to 10%. The identification of patients at risk who may benefit from antithrombotic therapy remains a challenge, and it is currently based on age and history of thrombotic events. However, the predictive value of these clinical characteristics is rather limited. Few prospective studies and even fewer interventional randomized studies are available, and there are no studies designed to formally validate the use of risk stratification. The implementation of laboratory parameters such as leukocytosis and/or the JAK2 V617F mutation into a scoring system may be of interest. The mechanisms at work leading to thrombosis remain largely speculative, but are likely to be complex and multifactorial, with a prominent role of cell-cell interactions, mostly owing to qualitative changes. The long-term treatment options to prevent thrombosis are, schematically, aspirin alone as primary prevention for the low-risk patients, and cytoreduction combined with aspirin for the other patients. In very low-risk young essential thrombocythemia patients, abstention can even be considered. The optimal duration of anticoagulation after a thrombotic event is not established. All antithrombotic therapies should be balanced with the hemorrhagic risk, which can also be increased in these patients.

Austrian consensus on the definition and treatment of portal hypertension and its complications (Billroth II)

In November 2004, the Austrian Society of Gastroenterology and Hepatology (ÖGGH) held for the first time a consensus meeting on the definitions and treatment of portal hypertension and its complications in the Billroth-Haus in Vienna, Austria (Billroth I-Meeting). This meeting was preceded by a meeting of international experts on portal hypertension with some of the proponents of the Baveno consensus conferences (http://www.oeggh.at/videos.asp). The consensus itself is based on the Baveno III consensus with regard to portal hypertensive bleeding and the suggestions of the International Ascites Club regarding the treatment of ascites. Those statements were modified by new knowledge derived from the recent literature and also by the current practice of medicine as agreed upon by the participants of the consensus meeting. In October 2011, the ÖGGH organized the second consensus meeting on portal hypertension and its complications in Vienna (Billroth II-Meeting). The Billroth II-Guidelines on the definitions and treatment of portal hypertension and its complications take into account the developments of the last 7 years, including the Baveno-V update and several key publications.

Polycythemia vera: gender-related phenotypic differences

In polycythemia vera, gender has recently been shown to influence the JAK2(V617F) allele burden, but its effect on the disease phenotype is unknown. This issue was investigated using the database of the European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP) Study. The ECLAP Study recruited 1,638 polycythemic subjects and followed for 2.7 ± 1.3 years. At study entry, men, compared to women, had a higher prevalence of myocardial infarction (11.3 vs. 5.8%; P < 0.0001) and peripheral arterial disease (6.1 vs. 2.9%; P < 0.05) while a history of venous thrombosis was more common in women (11.4 vs. 7.9%, P = 0.016). Among 234 venous thrombosis, there were 39 splanchnic vein thromboses (33 extra-hepatic portal vein thromboses and 6 Budd-Chiari syndromes). Most of these events occurred as an early disease presentation in young female subjects. Women, compared to men, had higher platelet counts (average value 430 ± 213 vs. 375 ± 201 × 10(9)/L; P < 0.0001) and lower hematocrits (0.46 ± 0.06 vs. 0.48 ± 0.06 l/l; P < 0.0001). Cholesterol plasma level, available in 995 subjects (61%), was lower in male patients (180.8 ± 43.1 vs. 196 ± 46.6 mg/dl; P < 0.0001). During follow-up there were 205 major thromboses confirming an high incidence of myocardial infarction in men although not statistically significant (1.2 vs. 0.6 cases per 100 person-years; P > 0.05). These data show several gender-related differences both in the thrombotic diathesis and in the prevalence of vascular risk factors of PV patients.

Myeloproliferative neoplasms in Budd-Chiari syndrome and portal vein thrombosis: a meta-analysis

Myeloproliferative neoplasms (MPNs) are the most common cause of Budd-Chiari syndrome (BCS) and nonmalignant, noncirrhotic portal vein thrombosis (PVT). In this meta-analysis, we determined the prevalence of MPNs and their subtypes as well as JAK2V617F and its diagnostic role in these uncommon disorders. MEDLINE and EMBASE databases were searched. Prevalence of MPNs, JAK2V617F, and MPN subtypes were calculated using a random-effects model. A total of 1062 BCS and 855 PVT patients were included. In BCS, mean prevalence of MPNs and JAK2V617F was 40.9% (95% CI, 32.9%-49.5%) and 41.1% (95% CI, 32.3%-50.6%), respectively. In PVT, mean prevalence of MPNs and JAK2V617F was 31.5% (95% CI, 25.1%-38.8%) and 27.7% (95% CI, 20.8%-35.8%), respectively. JAK2V617F and MPNs were more frequent in BCS compared with PVT (P = .03 and P = .09, respectively). Polycythemia vera was more prevalent in BCS than in PVT (P = .001). JAK2V617F screening in splanchnic vein thrombosis (SVT) patients without typical hematologic MPN features identified MPN in 17.1% and 15.4% of screened BCS and PVT patients, respectively. These results demonstrate a high prevalence of MPNs and JAK2V617F in SVT patients and show differences in underlying etiology between these disorders. Furthermore, these results validate routine inclusion of JAK2V617F in the diagnostic workup of SVT patients.

Venous thromboembolism in patients with essential thrombocythemia and polycythemia vera

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms (MPNs), which generally follow a benign and indolent clinical course. However, venous thromboses are common and constitute the main cause of morbidity and mortality. The discovery of the JAK2V617F mutation and other biomarkers has advanced our understanding of these diseases. There is a strong association between the presence of the JAK2V617F mutation and the development of thrombosis in ET. If venous thrombosis presents with unusual manifestations, the diagnosis of a MPN, such as PV or ET, should be part of the differentials. Treatment of venous thrombosis in MPN follows the same principle as in other patients with venous thrombosis, but careful attention to primary and secondary prophylaxis in addition to heparin-induced thrombocytopenia should be given. Cytoreductive therapy is indicated in high-risk subgroups of PV and ET patients, and alternative therapeutic agents have different effects on risk of venous thrombosis. New therapeutic approaches are emerging, and JAK2 inhibitors, histone deacetylase inhibitors and next-generation anticoagulants are in various stages of clinical development for the treatment of MPN, but their exact role in thrombosis prevention and treatment remains unclear.

Meta-analysis: the significance of screening for JAK2V617F mutation in Budd-Chiari syndrome and portal venous system thrombosis

BACKGROUND

It is important to evaluate whether screening for JAK2V617F mutation should be routinely performed in patients with Budd-Chiari syndrome (BCS) and portal venous system thrombosis (PVST). However, the prevalence of JAK2V617F mutation in such patients is substantially varied, and its association with development of myeloproliferative disorders (MPD) is deficiently identified.

AIMS

To estimate the prevalence of JAK2V617F mutation and to explore the significance of screening for JAK2V617F mutation in these patients.

METHODS

All observational studies regarding the prevalence of JAK2V617F mutation in patients with BCS and PVST were identified via PubMed and MEDLINE databases. Primary items were the proportions of JAK2V617F mutation and MPD.

RESULTS

Twenty-three studies fulfilled the inclusion criteria. Regardless of underlying aetiological factors, the pooled prevalence of JAK2V617F mutation was 37% and 24% in patients with BCS and PVST respectively. After pre-existing MPD was excluded, the pooled prevalence was decreased to 26% and 19%. Heterogeneity among studies was significant for the prevalence of JAK2V617F mutation. Compared with healthy subjects and patients with thrombosis in other sites, the prevalence of JAKV617F mutation was significantly higher in patients with BCS and PVST. The prevalence of MPD was significantly higher in patients with JAK2V617F mutation than those without.

CONCLUSIONS

JAK2V617F mutation is frequently found in patients with BCS and PVST, but there is a huge variation of prevalence among the included studies. Additionally, it is more specific to thrombosis in splanchnic areas and strongly associated with the development of MPD in these patients. Further studies are needed to evaluate whether the screening test should be widely performed in Asian countries and cirrhotic patients.

The prevalence of the activating JAK2 tyrosine kinase mutation in chronic porto-splenomesenteric venous thrombosis

BACKGROUND

Occult myeloproliferative disorders (MPD) are present in 25% of patients with chronic portal, splenic and mesenteric venous thrombosis (PSMVT). A somatic mutation of JAK2 (JAK2V617F) can be used to identify patients with latent MPD.

AIM

We evaluated the prevalence and clinical significance of JAK2V617F in patients with chronic PSMVT.

METHODS

Allele-specific polymerase chain reaction was performed to screen for JAK2V617F.

RESULTS

Thirty-five patients were tested for JAK2V617F. The underlying pro-coagulant condition was MPD in seven of 35 (20.0%) patients; other aetiologies included hereditary thrombophilia (n = 5), chronic pancreatitis (n = 2), liver abscess (n = 1) and umbilical vein sepsis (n = 3). The remainder were labelled idiopathic, i.e. 17/35 (48.6%) patients. JAK2V617F was detected in 16/35 (45.7%) patients: seven of seven (100%) with MPD, two of 11 (18.1%) with non-MPD acquired conditions and seven of 17 (41.2%) with 'idiopathic' chronic PSMVT. Mean haemoglobin concentration (P = 0.04), haematocrit (P = 0.04), white cell count (P = 0.002) and platelet count (P = 0.05) were significantly higher in patients with JAK2V617F. None of the seven patients with latent MPD have progressed to overt MPD over median follow-up of 85 months.

CONCLUSION

JAK2V617F occurs in 41% of patients with idiopathic chronic portal, splenic and mesenteric venous thrombosis, confirming the presence of latent myeloproliferative disorders, and should form part of the routine pro-coagulant screen.