Myeloproliferative neoplasms and splanchnic vein thrombosis: Clinical and molecular features. A single-center cohort study

Venous thromboses account for approximately 30-40% of vascular complications in MPN, also involving the splanchnic circulation (SVT) with a prevalence of 1-23%. Here, we reported a consecutive single-center series of 54 MPN patients (pts), who developed an SVT at diagnosis or during follow-up between 1979 and 2020. We identified 13% of PV, 16.7% of ET, 44.4% of MF, and 25.9% of MPN-U. Most of the cases (83.3%) bear a JAK2V617F mutation, whereas seven (13%) pts were characterized by other molecular markers, i.e., MPL in four and CALR mutations in three cases. The remaining two (3.7%) pts were defined as triple-negative. NGS was performed in 17 (31.5%) cases: the most frequent mutations were found in TET2 (35.3%) and DNMT3A (23.5%) genes, whereas seven (41.2%) pts had no additional mutation. At the time of SVT onset, active antiplatelet therapy was documented in 18.5% of the cases. Among the 16 (29.6%) pts who suffered from SVT during follow-up, cytoreduction was already on-going in 56.3% of the cases, whereas it was then started in all but 16 pts, mainly due to a normal blood cells count. Anticoagulants were started in 43 (79.6%) pts, including ten (18.5%) cases treated with DOACs. After a median follow-up from MPN diagnosis of 8.3 years, nine (16.7%) deaths were recorded: it was due to leukemic transformation in five pts, hemorrhages in three and infections in the remaining patient. 38.9% of the pts suffered from recurrent vascular events, either involving the arterial (13%) or the venous district (25.9%), with 10 (18.5%) pts experiencing a recurrent SVT. In the present study MPN-U seems to represent a distinct clinical entity when compared to other MPN subtypes, as SVT was the initial manifestation in all these cases. Interestingly, during follow-up none of these pts developed clinical features which enabled physicians to re-classify them among one of the classical MPN. Being aware of its limitations, our study confirm that SVT associated with MPN-U represents a more indolent disease as compared with full-diagnosed MPN. Notably, all leukemic evolutions were reported among MF pts after a median follow-up of 15.6 years. Furthermore, our preliminary data support the use of NGS analysis in MPN-related SVT management as it can provide useful diagnostic and prognostic information. However, more than one third of our pts developed recurrent vascular events, confirming the limited efficacy of conventional therapeutic approaches. Updated results will be presented.