Michelle A. Elliott

Thrombosis and haemorrhage in polycythaemia vera and essential thrombocythaemia

Despite decades of clinical and laboratory research, relatively little has been accomplished concerning the pathogenesis as well as the identification of risk factors for thrombosis and bleeding in myeloproliferative disorders. In polycythaemia vera, the pro‐thrombotic effect of an elevated haematocrit is well established. In contrast, thrombocytosis per se has not been similarly incriminated in essential thrombocythaemia. In both conditions, advanced age and the presence of a prior event identify thrombosis‐prone patients. There is increasing evidence to suggest an additional role by leucocytes that might partly explain the antithrombotic effects of myelosuppressive therapy. A substantial minority of affected patients display reduced levels of high molecular weight von Willebrand protein in the plasma during extreme thrombocytosis and it is believed that this might explain the bleeding diathesis of such patients. Recent controlled studies support the therapeutic value of hydroxyurea and aspirin in essential thrombocythaemia and polycythaemia vera, respectively. The current communication will address the incidence, phenotype, pathogenesis, risk factors, prevention, and treatment of both thrombosis and haemorrhage in these disorders.

Imatinib for systemic mast-cell disease

Imatinib has shown to be effective against malignant disease driven by ckit. We prospectively treated 12 adults with symptomatic systemic mast-cell disease at a dose of either 100 mg or 400 mg per day. Of the ten patients who we could assess for response, five (50%) had a measurable response to the drug, four of whom had important mast-cell cytoreduction and two who had complete clinical and histological remission. In the five patients with eosinophilia, three had complete clinical and haematological remission. The other two, who did not respond to treatment, were the only patients with the ckit D816V mutation. Our results suggest that imatinib either inhibits the growth-promoting role of wild type ckit, or targets an oncogenic kinase.

The clinical phenotype of wild-type, heterozygous, and homozygous JAK2V617F in polycythemia vera

Several studies have recently reported on the occurrence of a JAK2V617F mutation in myeloid cells from the majority of patients with polycythemia vera (PV). The clinical relevance of this novel observation currently is under study.

Splenic irradiation for symptomatic splenomegaly associated with myelofibrosis with myeloid metaplasia

Twenty‐three patients who had myelofibrosis with myeloid metaplasia (MMM) were treated at our institution with 50 courses of splenic irradiation (SI) for symptomatic splenomegaly. The median dose of radiation per course was 277.5 cGy, administered in a median of 7.5 fractions. 8/23 patients received multiple courses of SI. Of 49 evaluable courses of SI, 46 (93.9%) resulted in an objective decrease in spleen size. The median duration of response was 6 months (range 1–41). Reduction in spleen size was associated with symptomatic relief in all patients. Overall median survival after SI was 22 months. Significant cytopenia occurred in 10 (43.5%) patients, or 16 (32%) of the 50 courses of SI. Prolonged, life‐threatening pancytopenia after a single course of SI occurred in six patients (26%), resulting in fatal sepsis or haemorrhage in three (13%). Nine patients underwent subsequent splenectomy; the perioperative mortality rate was 11%. One third of patients experienced postoperative intra‐abdominal haemorrhage necessitating surgical re‐exploration. SI can provide symptomatic relief and a reduction in spleen size in most MMM patients. The increased risk of postoperative bleeding in patients requiring subsequent splenectomy dictates against considering SI as an alternative to splenectomy for patients who are otherwise good surgical candidates.

Thrombotic Thrombocytopenic Purpura and Hemolytic Uremic Syndrome

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are multisystemic disorders that are characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic manifestations, resulting from platelet agglutination in the arterial microvasculature. Until the introduction of plasma-based therapy, TTP was associated with a mortality rate greater than 90%. Current outcomes of TTP and HUS have improved dramatically with the use of plasma exchange, which should be initiated promptly at diagnosis. Recent evidence suggests that deficiency of a specific plasma protease responsible for the physiologic degradation of von Willebrand factor plays a pathogenic role in a substantial proportion of familial and acute idiopathic cases of TTP. Although multiple triggers, such as infection, drugs, cancer, chemotherapy, bone marrow transplantation, and pregnancy, are recognized, knowledge of the pathogenesis of TTP and HUS in relationship to these disorders remains incompletely understood and continues to evolve. While uncommon, TTP and HUS are of considerable clinical importance because of their abrupt onset, fulminant clinical course, and high morbidity and mortality in the absence of early recognition and treatment.

Thalidomide treatment in myelofibrosis with myeloid metaplasia

Summary.  Myelofibrosis with myeloid metaplasia (MMM) is uniquely characterized by macroscopic bone marrow stromal changes that are believed to be both reactive and cytokine mediated. Furthermore, a prognostically detrimental increase in bone marrow angiogenesis has recently been demonstrated. These observations suggest a potential therapeutic role for agents that are inhibitory to angiogenesis as well as cytokines that are pathogenetically implicated in MMM. In a prospective study of 15 patients with MMM, thalidomide treatment, starting at a dose of 200 mg/d, resulted in increased platelet counts (12 of 15 patients), increased haemoglobin level (3 of 15), a modest decrease in spleen size (3 of 12), increased bone marrow megakaryopoiesis (5 of 9) and decreased bone marrow angiogenesis (2 of 9). Undesirable haematological effects included pericardial extramedullary haematopoiesis in one patient, marked leucocytosis in two patients and extreme thrombocytosis in three patients. The thrombocytosis occurred in both patients with post‐thrombocythaemic myeloid metaplasia (PTMM) and was also associated with higher baseline levels of circulating CD34+ cells. Previously described toxicities of thalidomide were seen in the majority of patients and dose escalation to 400 mg/d was permitted in only two patients. In contrast, toxicity‐related dose reductions to 50 mg/d did not appear to lessen drug efficacy. We conclude that thalidomide has both beneficial and potentially adverse biological activity in MMM. A lower dose of the drug might be more tolerable without compromising therapeutic value. Patients with PTMM and/or markedly increased circulating CD34+ cell counts might be susceptible to thalidomide‐induced thrombocytosis.

CSF3R T618I is a highly prevalent and specific mutation in chronic neutrophilic leukemia

Truncation mutations of the receptor cytoplasmic domain for colony-stimulating factor 3 (CSF3R) are frequently seen in severe congenital neutropenia, whereas activating missense mutations affecting the extracellular domain (exon 14) have been described in hereditary neutrophilia and chronic neutrophilic leukemia (CNL). In order to clarify mutational frequency, specificity and phenotypic associations, we sequenced CSF3R exons 14–17 in 54 clinically suspected cases of CNL (n=35) or atypical chronic myeloid leukemia (aCML; n=19). Central review of these cases confirmed WHO-defined CNL in 12 patients, monoclonal gammopathy (MG)-associated CNL in 5 and WHO-defined aCML in 9. A total of 14 CSF3R mutations were detected in 13 patients, including 10 with CSF3RT618I (exon 14 mutation, sometimes annotated as CSF3R T595I). CSF3RT618I occurred exclusively in WHO-defined CNL with a mutational frequency of 83% (10 of 12 cases). CSF3R mutations were not seen in aCML or MG-associated CNL. CSF3RT618I was also absent among 170 patients with primary myelofibrosis (PMF; n=76) or chronic myelomonocytic leukemia (CMML; n=94). SETBP1 mutational frequencies in WHO-defined CNL, aCML, CMML and PMF were 33, 0, 7 and 3%, respectively. Four CSF3RT618I-mutated cases co-expressed SETBP1 mutations. We conclude that CSF3RT618I is a highly sensitive and specific molecular marker for CNL and should be incorporated into current diagnostic criteria.

Posttransplantation thrombotic thrombocytopenic purpura: a single-center experience and a contemporary review.

OBJECTIVE To assess the activity of von Willebrand factor-cleaving protease (vWF-CP) in patients with thrombotic thrombocytopenic purpura (TTP) complicating bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT). PATIENTS AND METHODS From March 1, 1999, to June 30, 2001, allogeneic and autologous hematopoietic stem cell transplantation was performed in 118 and 400 patients, respectively. We reviewed risk factors for development of posttransplantation TTP and measured vWF-CP activity during active TTP in 10 recipients. RESULTS The incidence of TTP after allogeneic and autologous transplantation was 6.8% (8/118) and 0.25% (1/400), respectively. Among the allogeneic transplant recipients, the incidence of TTP after nonmyeloablative (NMA) PBSCT, matched unrelated donor BMT, and sibling BMT or PBSCT was 15.4% (2/13), 11.8% (2/17), and 4.5% (4/88), respectively. Of the 10 patients with TTP, 9 (90%) had received extensive prior therapy, including autologous transplantation in both NMA recipients. Acute graft-vs-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate in most affected patients. The vWF antigen level was elevated in all patients, and no patients showed evidence of vWF-CP deficiency. During active TTP, 6 patients had grade II-IV acute GVHD, 1 had extensive chronic GVHD, and 4 had cytomegalovirus viremia. Risk factor analysis for development of TTP showed that transplant type (NMA and matched unrelated donor) and source of stem cells (bone marrow vs peripheral blood stem cell) were significant. CONCLUSIONS Posttransplantation TTP was not found to be associated with severe vWF-CP deficiency. The elevated levels of vWF antigen are consistent with diffuse endothelial injury likely because of multiple interacting factors such as extensive prior therapy, GVHD, cyclosporine, and reactivation of cytomegalovirus. The disorder appears to be more frequent among patients with, or at risk for, acute GVHD, suggesting a possible role in the pathogenesis. Nonmyeloablative transplantation does not appear to confer a lesser risk, possibly for these reasons.

Risk-adjusted manipulation of melphalan dose before stem cell transplantation in patients with amyloidosis is associated with a lower response rate.

Summary:High-dose chemotherapy and autologous stem cell transplantation are used increasingly to treat patients with light-chain-related amyloidosis (AL). Treatment-related mortality is approximately 15%. To enable more patients to undergo stem cell transplantation, a risk-adapted strategy has been developed to treat with lower chemotherapy doses those patients who are at excessive risk. It is unclear whether reducing the chemotherapy dose in patients at excessive risk of treatment toxicity reduces the overall response. We retrospectively reviewed 171 AL patients who underwent conditioning chemotherapy with stem cell transplantation. The patients comprised two groups: those receiving standard high-dose melphalan and those receiving intermediate-dose melphalan. Responses were categorized as hematologic response, which used criteria for myeloma response. The two groups showed statistically significant differences; the overall response rates were 75% in the high-dose group and 53% in the intermediate-dose group although treatment-related mortality was the same in both groups. Reducing the melphalan dose appeared to render more AL patients eligible for stem cell transplantation but sacrificed an element of response. Methods are needed to reduce treatment-related toxicity so that more patients can receive full-dose conditioning chemotherapy.

JAK2 germline genetic variation affects disease susceptibility in primary myelofibrosis regardless of V617F mutational status: Nullizygosity for the JAK2 46/1 haplotype is associated with inferior survival

A common JAK2 germline haplotype (46/1) has been associated with JAK2V617F (VF)-positive myeloproliferative neoplasms. The rs12343867 SNP (C/T) tags this haplotype. A total of 130 patients (77 VF-positive) with primary myelofibrosis (PMF) were analyzed for this informative SNP, using bone marrow-derived DNA. The observed 46/1 C allele frequencies in VF-positive (50%) and VF-negative (36%) patients were both significantly higher than expected in population controls (P<0.01). Genotype distributions in VF-positive/VF-negative patients were CC 31%/9%, CT 38%/53% and TT 31%/38% (P=0.01). CC genotype/C-allele frequencies in patients with <20% VF mutation burden (12%/37%) were similar (P=0.95) to those seen in VF-negative patients (9%/36%), but were significantly lower (P<0.01) than those seen in the presence of >50% mutation burden (∼67%/71%). The rs12343867 genotype did not correlate with the International Prognostic Scoring System (IPSS) score or karyotype. Unexpectedly, the TT genotype was associated with shortened survival (P<0.01), which was not accounted for by IPSS score or VF allele burden. We conclude that JAK2 germline genetic variation affects disease susceptibility, and possibly survival, in PMF, regardless of VF mutational status. Allelic distortion from acquired uniparental disomy contributes to the appearance of a more pronounced effect on disease susceptibility in VF-positive patients, when studying clonally affected tissue.