Thrombophilic genotypes, natural anticoagulants, and plasma homocysteine in myeloproliferative disorders: relationship with splanchnic vein thrombosis and arterial disease.

The contribution of pro-thrombotic factors towards the development of arterial disease (AD) and splanchnic vein thrombosis (SVT) was retrospectively evaluated in 79 patients (39M, 40F, mean age 55 +/- 16 years) with myeloproliferative disorders (MPD) (essential thrombocythemia [n = 26], primary proliferative polycythemia [n = 27], and idiopathic myelofibrosis [n = 26]). Of these, 18 had AD and 17 SVT, the remaining 44 were non-thrombotic (NT). Plasma concentrations of natural anticoagulants, plasma homocysteine (HC), IgG anticardiolipin antibodies (aCL), and thrombophilic genotypes (methylenetetrahydrofolate reductase C(677)T, factor V Leiden, prothrombin G(20210)-->A) were determined. Isolated protein C deficiency was found in 23% of patients from the SVT group, in 5% from the AD group, in 6.8% from the NT group, and in 1% of historical controls (P = 0.0001). The prevalence of thrombophilic genotypes and that of the other natural anticoagulants did not differ across the groups. The proportion of patients with elevated plasma HC was 66% in the AD group, 27% in the non-thrombotic group, 12% in the SVT group and 4.5% in the control group (P < 0.0001). Patients with AD had higher plasma HC (24.4 +/- 23 micromol/L) than NT patients (12.3 +/- 7.7 micromol/L), SVT patients (9 +/- 4.9 micromol/L), and healthy controls (7.9 +/- 3 micromol/L) (P < 0.0001). In a logistic regression model lower protein C was independently associated with SVT, whereas elevated plasma HC was independently associated with AD. Measurement of plasma HC and protein C in MPD may identify patients more likely to suffer arterial disease and splanchnic vein thrombosis and who may require plasma HC lowering in the former case.