SYTHROM Cohort, Myeloproliferative Neoplasia With Normal CBC and Thrombotic Complications
SYTHROM Cohort, Myeloproliferative Neoplasia With Normal CBC and Thrombotic Complications
Among the etiologies of thrombosis, myeloproliferative neoplasia (MPN) is quite rare but
 should be investigated in case of thrombosis of atypical localization (digestive or cerebral)
 or in the context of recurrent idiopathic thrombosis in a young subject. Thrombosis could
 reveal an underlying MPN through the identification of a JAK2 V617F mutation. Rarely, MPN
 with thrombotic complications present with normal complete blood count(CBC). In case of a MPN
 with a thrombotic event but without CBC abnormality, anti-thrombotic treatment is
 recommended. But there is no recommendation for the indication of cytoreductive therapy and
 the clinician's decision is often empirical.

 One of the major complications of for essential thrombocythemia (ET) or polycythemia vera
 (PV) is thrombosis and an age over 60 is a major risk factor. The treatment of thrombosis
 associated with TE or PV is based on recommendations the main therapeutic objective of which
 is to reduce the thrombotic risk. The combination of a cytoreducing agent and antithrombotic
 treatment is thus proposed in high-risk patients. The efficacy of this management is
 monitored by assessing CBC with the objective of normalization at <400 G/L of platelets for
 ET patients and <45% hematocrit in case of PV.

 The absence of abnormal CBC makes it difficult to justify cytoreduction. The benefit of such
 a therapy in this context has not been clinically demonstrated. If a cytoreductive therapy is
 initiated, no biological parameters are available to assess the response to treatment.

 The objective of this observational study is to evaluate the incidence of recurrence of
 thrombosis in patients whose thrombotic event revealed an underlying MPN with normal CBC. A
 comparison of groups treated or not with cytoreductive agents will be performed. Longitudinal
 monitoring of the patients will provide a better understanding of the nature and kinetics of
 hematological changes in these patients.
This study is observational and multicentric.In a first part, patients will be
 retrospectively included. Baseline clinical and biological data obtainedat the time of MPN
 diagnosis of MPN with normal CBC following venous or arterial thrombosis will be recorded and
 follow-up data will be collected in an e-CRF. In a second part, patients will be included
 prospectively and diagnostic and follow-up data will be collected. Whether or not to initiate
 treatment with a cytoreduction treatment is left to the discretion of the clinician.
Inclusion Criteria :

 -  Adult ≥18 years old

 -  Diagnosis of a deep arterial or venous thrombotic event verified by imaging (Doppler
 or CT scan)

 -  Diagnosis of MPN with normal CBC according to WHO 2017 criteria characterized by the
 detection of a molecular abnormality JAK2V617F mutation (regardless of allelic load),
 CALR or MPL and/or a bone marrow biopsy with abnormalities in favor of MPN.

 -  Normal blood cell count not suggestive of polycythemia vera (hematocrit<48% and
 hemoglobin<16g/dL for women; hematocrit<49% and hemoglobin<16.5g/dL for men),
 essential thrombocythemia (platelets<450 G/L) nor myelofibrosis (white blood cell
 count<11 G/L, no anemia or erythromyelemia associated with splenomegaly) at the time
 of the thrombotic event.

 Exclusion Criteria :

 -  Minors (<18 years of age)

 -  Microcirculation disorders (erythromelalgia, headaches, paresthesia, ischemia of the
 extremities)

 -  Superficial or deep arterial or venous thrombosis NOT verified by imaging

 -  Diagnosis or history of TE, PV or myelofibrosis at time of first thrombotic event

 -  Diagnosis of mixed myelodysplastic/myeloproliferative syndrome

 -  Diagnosis of unclassifiable MPN with excess blasts at the onset or signs of
 myelodysplasia as defined by the WHO 2017 classification