Quand évoquer un syndrome myéloprolifératif en pathologie vasculaire ?

Thrombotic events are frequent in polycythemia vera (PV) and in essential thrombocythemia (ET). The frequency of thrombotic complications at presentation of PV and ET is nearly 50 %. The spectrum of thrombotic complications is broad: thrombosis of arteries, veins and microvessels have been reported. Venous thrombosis can involve all territories but PV and TE are the commonest underlying etiology for Budd-Chiari Syndrome and splanchnic veins thrombosis. Endogenous erythroid-colony formation may be seen in up to 78 % of patients thought to have Budd Chiari Syndrome and in 48 % of splanchnic veins thrombosis. Major arterial thrombotic complications occur in 20 %, especially in the extremities and in cerebral circulation. Microcirculatory disturbances are common in ET, occurring in 29 % at presentation and 27 % during follow up. In the extremities, erythromelalgia, a characteristic syndrome of red and congested extremities with raised temperature and painful burning sensations, is noticed in 30 to 50 % of TE. Other microcirculatory manifestations like acrocyanosis, blue toes, digital gangrene can occur. All of these manifestations are highly sensitive to aspirin. Cerebral microcirculatory symptoms occur in about one-third of patients: migraine, transient visual symptoms like scotomata, blurred vision are characterized by a sudden onset, a short duration and a sequential course. Three kinds of leg ulcers have been described: leg ulceration as a consequence of microcirculatory thrombosis, exceptionnally, pyoderma gangrenosum, and leg ulcers attributed to side effects of hydroxyurea. Microcirculatory leg ulcers are the most common: they are painful, inflammatory and sometimes, necrotic. They heal with treatment of SMP. Hydroxyurea-induced leg ulcers are painful, fibrous and multiple in 60 %. Cessation of hydroxyurea typically leads to wound healing. The Polycythemia Vera Study Group (PVSG) established diagnostic criteria for PV and TE. Because SMP can have incompletely expressed disease, other authors have proposed determination of serum erythropoietin, examination of bone marrow histology, and spontaneous endogenous colony assays for diagnosis of PV or TE. The individual thrombotic risk depends on elevated hematocrit for PV, age (> 60) and prior thrombosis for PV and TE. Congenital and acquired (antiphospholipid syndrome) thrombotic states probably increase the risk of thrombosis. (J Mal Vasc 2005; 30: 46-52).