In a series of 218 subjects diagnosed as having nonleukemic chronic myeloproliferative disorders in a single institution within a 18-year period, 13 instances of acute transformation were registered. They corresponded to 8 out of 70 patients with idiopathic myelofibrosis (IM), 4 out of 91 with polycythemia vera (PV), and 1 out of 57 with essential thrombocythemia (ET). The actuarial probability of developing such a complication at 100 months from diagnosis reached 20.6% in IM, 8.7% in PV, and 4% in ET. Only 1 IM patient whose condition developed into acute leukemia had received prior cytolytic therapy, whereas, in contrast, all PV and ET patients showing this pattern had previously been treated with either ³²P or alkylating agents. On the other hand, acute transformation in IM generally had an insidious presentation, contrasting with its abrupt onset in most PV and ET patients. Most acute leukemias (12 out of 13) exhibited a myeloid phenotype. The patients’ median survival from diagnosis of the acute transformation was only 3 months, the development of this complication significantly shortening the patients’ overall survival.

SummaryRecent reports have described the factor XIII A subunit (FXIII-A) Val34Leu polymorphism as a protective factor against venous and arterial thrombosis. The aim of this study was to investigate the association between the FXIII-A Val34Leu polymorphism, its interaction with fibrinogen concentration, and thrombosis in patients with antiphospholipid antibodies (aPL). We included 172 consecutive patients with aPL: 88 with primary antiphospholipid syndrome (APS), 38 with APS associated with systemic lupus erythematosus (APS-SLE), 32 with SLE and aPL but without APS (SLE-aPL), and 14 asymptomatic individuals with aPL (A-aPL). The FXIII-A Val34Leu polymorphism was assessed by polymerase chain reaction techniques. We found no significant differences in FXIII-A Leu34 allele frequencies between primary APS (allele frequency 0.22), APS-SLE (0.23), SLE-aPL (0.22) and A-aPL (0.32) patients, or between patients with (0.21) and without thrombosis (0.26). FXIII-A Leu34 allele frequencies were significantly lower in patients with thrombosis and those in the upper fibrinogen tertile (>3.40 g/l) (allele frequency 0.07) compared with patients without thrombosis in the upper fibrinogen tertile (0.29) and patients with (0.29) and without (0.25) thrombosis in the mid- and lower fibrinogen tertiles. The FXIII-A Leu34 allele had a protective effect against thrombosis in patients in the upper fibrinogen tertile (odds ratio [OR]=0.20, 95% confidence interval [CI] 0.07–0.60) but not in those in the other tertiles (OR=1.20, 95% CI 0.67–2.16). The FXIII-A Leu34 allele seems to have a protective effect on the development of thrombosis in patients with aPL, but only in those with high plasma fibrinogen values.

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