Myeloproliferative and thrombotic burden and treatment outcome of thrombocythemia and polycythemia patients

Prospective studies indicate that the risk of microvascular and major thrombosis in untreated thrombocythemia in various myeloproliferative neoplasms(MPN-T) is not age dependent and causally related to platelet-mediated thrombosis in early, intermediate and advanced stages of thrombocythemia in MPN-T. If left untreated both microvascular and major thrombosis frequently do occur in MPN-T, but can easily be cured and prevented by low dose aspirin as platelet counts are above 350 × 109/L. The thrombotic risk stratification in the retrospective Bergamo study has been performed in 100 essential thrombocythemia(ET) patients not treated with aspirin thereby overlooking the discovery in 1985 of aspirin responsive platelet-mediated arteriolar and arterial thrombotic tendency in MPN-T disease of ET and polycythemia vera(PV) patients. The Bergamo definition of high thrombotic risk and its persistence in the 2012 International Prognostic Score for ET is based on statistic mystification and not applicable for low and intermediate MPN-T disease burden in ET and PV patients on aspirin. With the advent of molecular screening of MPN patients, MPN-T disease associated with significant leukocytosis, thrombocytosis, constitutional symptoms and/or moderate splenomegaly are candidates for low dose peglyated interferon(Pegasys R, 45 mg/m L once per week or every two weeks) as the first line myeloreductive treatment option in JAK2V617 F mutated MPN-T disease in ET and PV patients. If non-responsive to or side effects induced by IFN, hydroxyurea is the second line myelosuppressive treatment option in JAK2V617 F mutated ET and PV patients with increased MPN-T disease burden.

European vs 2015-World Health Organization clinical molecular and pathological classification of myeloproliferative neoplasms

The BCR/ABL fusion gene or the Ph^1-chromosome in the t(9;22)(q34;q11)exerts a high tyrokinase acticity,which is the cause of chronic myeloid leukemia(CML).The1990 Hannover Bone Marrow Classification separated CML from the myeloproliferative disorders essential thrombocythemia(ET),polycythemia vera(PV)and chronic megakaryocytic granulocytic myeloproliferation(CMGM).The 2006-2008 European Clinical Molecular and Pathological(ECMP)criteria discovered 3variants of thrombocythemia:ET with features of PV(prodromal PV),"true"ET and ET associated with CMGM.The 2008 World Health Organization(WHO)-ECMP and 2014 WHO-CMP classifications defined three phenotypes of JAK2^(V617F)mutated ET:normocellular ET(WHO-ET),hypercelluar ET due to increased erythropoiesis(prodromal PV)and ET with hypercellular megakaryocytic-granulocytic myeloproliferation.The JAK2^(V617F)mutation load in heterozygous WHO-ET is low and associated with normal life expectance.The hetero/homozygous JAK2^(V617F)mutation load in PV and myelofibrosis is related to myeloproliferative neoplasm(MPN)disease burden in terms of symptomaticsplenomegaly,constitutional symptoms,bone marrow hypercellularity and myelofibrosis.JAK2 exon 12mutated MPN presents as idiopathic eryhrocythemia and early stage PV.According to 2014 WHO-CMP criteria JAK2 wild type MPL^(515)mutated ET is the second distinct thrombocythemia featured by clustered giant megakaryocytes with hyperlobulated stag-horn-like nuclei,in a normocellular bone marrow consistent with the diagnosis of"true"ET.JAK2/MPL wild type,calreticulin mutated hypercellular ET appears to be the third distinct thrombocythemia characterized by clustered larged immature dysmorphic megakaryocytes and bulky(bulbous)hyperchromatic nuclei consistent with CMGM or primary megakaryocytic granulocytic myeloproliferation.

Aspirin responsive platelet thrombophilia in essential thrombocythemia and polycythemia vera

Essential thrombocythemia(ET) and polycythemia vera(PV) frequently present with erythromelalgia and acrocyanotic complications, migraine-like microvascular cerebral and ocular transient ischemic attacks(MIAs) and/or acute coronary disease. The spectrum of MIAs in ET range from poorly localized symptoms of transient unsteadiness, dysarthria and scintillating scotoma to focal symptoms of transient monocular blindness, transient mono- or hemiparesis or both. The attacks all have a sudden onset, occur sequentially rather than simultaneously, last for a few seconds to several minutes and are usually associated with a dull, pulsatile or migraine-like headache. Increased hematocrit and blood viscosity in PV patients aggravate the microvascular ischemic syndrome of thrombocythemia to major arterial and venous thrombotic complications. Phlebotomy to correct hematocrit to normal in PV significantly reduces major arterial and venous thrombotic complications, but fails to prevent the platelet-mediated erythromelalgia and MIAs. Complete long-term relief of the erythromelalgic microvascular disturbances, MIAs and major thrombosis in ET and PV patients can be obtained with low dose aspirin and platelet reduction to normal, but not with anticoagulation. Skin punch biopsies from the erythromelalgic area show fibromuscular intimal proliferation of arterioles complicated by occlusive plateletrich thrombi leading to acrocyanotic ischemia. Symptomatic ET patients with erythromelalgic microvascular disturbances have shortened platelet survival, increased platelet activation markers β-thromboglobulin(β-TG), platelet factor 4(PF4) and thrombomoduline(TM), increased urinary thromboxane B2(TXB2) excretion, and no activation of the coagulation markers thrombin fragments F1+2 and fibrin degradation products. Inhibition of platelet cyclooxygenase(COX1) by aspirin is followed by the disappearance and no recurrence of microvascular disturbances, increase in platelet number, correction of the shortened platelet survival times to normal, and reduction of increased plasma levels of β-TG, PF4, TM and urinary TXB2 excretion to normal. These results indicate that platelet-mediated fibromuscular intimal proliferation and platelet-rich thrombi in the peripheral, cerebral and coronary end-arterial microvasculature are responsible for the erythromelalgic ischemic complica-tions, MIAs and splanchnic vein thrombosis. Baseline platelet P-selectin levels and arachidonic acid induced COX1 mediated platelet activation showed a highly significant increase of platelet P-selectin expression(not seen in ADP and collagen stimulated platelets), which was significantly higher in JAK2V617 F mutated compared to JAK2 wild type ET.

Changing insights in the diagnosis and classification of autosomal recessive and dominant von Willebrand diseases 1980-2015

The European Clinical Laboratory and Molecular(ECLM) criteria define 10 distinct Willebrand diseases(VWD) recessive type 3, severe 1, 2C and 2N; dominant VWD type 1 secretion/clearance defect, 2A, 2B, 2E, 2M and 2D; and mild type 1 VWD(usually carriers of recessive VWD). Recessive severe 1 and 2C VWD are characterized by secretion and multimerization defects caused by mutations in the D1-D2 domain. Recessive 2N VWD is a mild hemophilia due to D'-FVIII-von Willebrand factor(VWF) binding site mutations. Dominant 2E VWD caused by heterozygous missense mutations in the D3 domain is featured by a secretion-clearancemultimerization VWF defect. Dominant VWD type 2M due to loss of function mutations in the A1 domain is characterized by decreased ristocetin-induced platelet aggregation and VWF RCo, normal VWF multimers and VWF CB, a poor response of VWF RCo and good response of VWF CB to desmopressin(DDAVP). Dominant VWD type 2A induced by heterozygous mutations in the A2 domain results in hypersensitivity of VWF for proteolysis by ADAMTS13 into VWF degradationproducts, resulting in loss of large VWF multimers with triplet structure of each individual VWF band. Dominant VWD type 2B due to a gain of function mutation in the A1 domain is featured by spontaneous interaction between platelet glycoprotein Ib(GPIb) and mutated VWF A1 followed by increased proteolysis with loss of large VWF multimers and presence of each VWF band. A new category of dominant VWD type 1 secretion or clearance defect due to mutations in the D3 domain or D4-C1-C5 domains consists of two groups Those with normal or smeary pattern of VWF multimers.

Pseudohemophilia of Erik von Willebrand caused by homozygous one nucleotide deletion in exon 18 of the VW-factor gene

The original description of a novel severe bleeding disorder as"Hereditary Pseudohemophilia"by Erik von Willebrand can currently be labelled as von Willebrand disease(VWD)type 3.VWD type 3 is autosomal recessive caused by homozygous or double heterozygous null mutations in the von Willebrand factor(VWF)gene and typically characterized by prolonged bleeding time and APTT,FⅧ:C levels below 2%,undetectable VWF:Ag,VWF:RCo and VWF:CB and absence of ristocetin induced platelet aggregation(RIPA).Autosomal recessive von Willebrand disease type 3 VWD with virtual complete VWF deficiency are homozygous or compound heterozygous for two null alleles(gene deletions,stop codons,frame shift mutations,splice site mutations,and absence of m RNA).Reports on severerecessive VWD compound heterozygous for a null allele and a missense mutation and homozygous or double heterozygous for missense mutations are associated with very low but measurable FⅧand VWF:Ag and should be reclassified as severe recessive type 1 VWD.Homozygous missense or compound missense/null mutations related to recessive severe type 1 VWD have been indentified in the VWF prosequence D1 and D2domains,the D4,B1-3,C1-2 domains,and only a very few in the dimmerization site(D3 domain).The detection of even tiny amounts of VWF:Ag after desmopressin acetate(DDAVP)or in hidden sites like platelets allows the differentiation between patients with VWD type 3 and homozygous or double heterozygous recessive severe type 1.Carriers of a null allele related to VWD type 3 or a missense mutation related with severe recessive type 1 VWD may present with mild VWD with low penetrance of bleeding in particular when associated with blood group O.Heterozygous obligatory carriers(OC)of a null mutation or a missense mutation related to recessive VWD type 3 or severe type 1both present with asymptomatic or mild VWD type 1 in particular when associated with blood group O.The response to DDAVP of OC of either a nonsense or a missense mutation appears to be abnormal and diagnostic with a 3-times higher response of FⅧ:C as compared to VWF:Ag.In contrast,the responses to DDAVP of FⅧ:C and VWF:Ag are equally good in individuals with low VWF levels related to blood group O and a normal VWF gene and protein(pseudo-VWD).These observations are completely in line with and extend the original observations of von Willebrand in a large family with VWD type 3 and asymptomatic or mild true type1 VWD in OC.