The authors retrospectively analyzed the initial characteristics, treatment, and clinical course in 147 patients with essential thrombocythemia (ET). Median age was 60 years and the M:F ratio was 0.69. At diagnosis, 53 patients were asymptomatic; 50 patients had functional symptoms (mainly vasomotor disturbances); 27 patients had large vessel thrombosis; 27 patients had a bleeding diathesis; and seven patients had both bleeding and thrombosis. The platelet count ranged from 0.7 to 2.92 X 10(12)/l. Forty-five of the 61 tested patients (61%) had prolonged bleeding time and/or platelet hypoaggregation. Three patients had in vitro spontaneous aggregation. No significant correlations were found between hemostatic findings and in vivo bleeding or thrombosis. The incidence of bleeding, however, was higher in patients with more than 2 x 10(12)/l platelets. Of 87 karyotypes performed with banding techniques, only four were abnormal. One hundred twenty-nine patients received one or more cytoreductive agents at diagnosis or during follow-up. Sixty patients received an antiaggregating agent. First-line therapy was radiophosphorus (32P) in 22 patients; busulfan in 35 patients; and hydroxyurea in 72 patients. Hydroxyurea required continuous maintenance therapy and had to be changed to another treatment in 12 of the initial responders because of inadequate control of thrombocythemia. During follow-up, 14 treated patients experienced one or several major thrombotic events. Two untreated patients also had major thrombosis. Only one major bleeding event was seen during follow-up. Median actuarial survival was 73.5% at 7 years and only one patient progressed to acute non-lymphocytic leukemia (ANLL). These results suggest that large vessel thrombosis is the main complication of ET. It appears largely unpredictable in a given patient at diagnosis but can be largely prevented by the control of thrombocythemia. Because of the low incidence of side effects of treatment in this experience, the authors believe that cytoreductive therapy is indicated in most patients with ET, as long as a group of patients with very low risk of thrombosis is not defined in prospective studies.

Treatment with alkylating agents or radiophosphorous (32P) has been shown to carry a certain leukemogenic risk in myeloproliferative disorders (MPDs), including essential thrombocytemia (ET). The leukemogenic risk associated to treatment with hydroxyurea in ET, on the other hand, is generally considered to be relatively low. Between 1970 and 1991, we diagnosed ET in 357 patients, who were monitored until 1996. One or several therapeutic agents had been admistered to 326 patients, including hydroxyurea (HU) in 251 (as only treatment in 201), pipobroman in 43, busulfan in 41, and32P in 40. With a median follow-up duration of 98 months, 17 patients (4.5%) had progressed to acute myeloid leukemia (AML; six cases) or myelodysplastic syndrome (MDS; 11 cases). Fourteen of these patients had received HU, as sole treatment in seven cases, and preceded or followed by other treatment in seven cases, mainly pipobroman (five cases). The remaining three leukemic progressions occurred in patients treated with 32P (two cases) and busulfan (one case). The incidence of AML and MDS after treatment, using 32P alone and 32P with other agents, busulfan alone and with other agents, HU alone and with others agents, and pipobroman alone and with other agents was 7% and 9%, 3% and 17%, 3.5% and 14%, and 0% and 16%, respectively. Thirteen of 17 patients who progressed to AML or MDS had successful cytogenetic analysis. Seven of them had rearrangements of chromosome 17 (unbalanced translocation, partial or complete deletion, isochromosome 17q) that resulted in 17p deletion. They also had a typical form of dysgranulopoiesis combining pseudo Pelger Hüet hypolobulation and vacuoles in neutrophils, and p53 mutation, as previously described in AML and MDS with 17p deletion. Those seven patients had all received HU, as the only therapeutic agent in three, and followed by pipobroman in three. The three patients who had received no HU and progressed to AML or MDS had no 17p deletion. A review of the literature found cytogenetic analysis in 35 cases of AML and MDS occurring after ET, 11 of whom had been treated with HU alone. Five of 35 patients had rearrangements that resulted in 17p deletion. Four of them had been treated with HU alone. These results show that treatment with HU alone is associated with a leukemic risk of approximately 3.5%. A high proportion of AML and MDS occurring in ET treated with HU (alone or possibly followed by pipobroman) have morphologic, cytogenetic, and molecular characteristics of the 17p− syndrome. These findings suggest that widespread and prolonged use of HU in ET may have to be reconsidered in some situations, such as asymptomatic ET.

The objective of this open label, phase 1-2, multicentre trial was to evaluate the safety of AMG 531, a novel thrombopoiesis-stimulating peptibody, and its effect on platelet counts in adults with immune thrombocytopenic purpura. Four patients were assigned to each of four unit-dose cohorts: 30, 100, 300 or 500 lg, administered subcutaneously on days 1 and 15 (or day 22 if the day 15 platelet count was >50 · 10 9 /l). Safety was assessed by adverse event (AE) monitoring, clinical laboratory studies and antibody assays. Platelet response was defined as a platelet count double the baseline value and between 50 and 450 · 10 9 /l. Sixteen patients (10 women) were enrolled. The 500-lg cohort was discontinued because the first patient's platelet count became unacceptably high. AEs were generally expected and mild or moderate; the most frequent was headache (eight of 16 patients). Two patients experienced serious AEs related to AMG 531 (severe headache and elevated serum lactic dehydrogenase; thrombocytopenia). Platelet responses occurred with all doses and with a dose equivalent to ‡1 lg/kg in eight of 11 patients. In summary, patients tolerated AMG 531 well at the doses tested. No anti-AMG or antithrombopoietin antibodies were detected. Doses equivalent to ‡1 lg/kg increased platelet counts.

Summary.In pregnant women with antecedents of autoimmune thrombocytopenia (AITP), no predictive factor for severe fetal thrombocytopenia has been identified. We evaluated the relationships between the course of the maternal disease before and during pregnancy and the risk of severe fetal thrombocytopenia, in 64 pregnant women with known chronic AITP antecedents, over a 12-year period. 28 pregnant women had undergone splenectomy before pregnancy and 17 experienced severe thrombocytopenia (< 50 × 10 9 /l) during pregnancy (monthly determination). Eight infants presented with severe thrombocytopenia at birth (12·5%), and four in the following days (6·25%). No severe haemorrhage was observed. Severe thrombocytopenia at birth was present in 57% (CI 95% 18-90%) of the infants born to mothers with severe pregnancy-associated thrombocytopenia and splenectomy antecedents, and in 0% (CI 95% 0-15%) of the infants born to mothers who presented none of these antecedents (P ¼ 0·001). In thrombocytopenic mothers the infant platelet counts at birth were positively correlated to the nadir maternal platelet count during the index pregnancy (r ¼ 0·42, P ¼ 0·0075).These results suggest that severe autoimmune disease is a risk factor for severe fetal thrombocytopenia, and that pregnant women with no antecedent of splenectomy nor severe thrombocytopenia during pregnancy have a very low risk of severe fetal thrombocytopenia.