Myeloproliferative disorders Clonal hematopoiesis (stem cell
disorder) Marrow hypercellularity Overproduction of one or more
cell lines (effective hematopoiesis) Exception: myelofibrosis
Differentiation nearly normal
Slide 2
The common bcr-abl negative myeloproliferative disorders
Polycythemia vera Essential thrombocythemia Myelofibrosis/myeloid
metaplasia
JAK-2 Tyrosine kinase involved in signaling pathways initiated
by EPO, TPO, G-CSF and other growth factors V617F mutations in most
cases of PV, ET, MF Other JAK-2 mutations (exon 12, etc) in a
minority of PV cases (almost all cases of PV have a JAK-2 mutation
of some type) Some cases of ET, MF lack JAK-2 mutation Mutation
releases cells from dependence on growth factors Homozygosity for
mutation seen mainly in P vera, associated with disease progression
Specific inhibitors of the kinase now in clinical trials
Slide 5
Structure-function relationships in the JAK2 receptor Science
2014; 344:703
Slide 6
In Panel A, in the absence of ligand, the erythropoietin
receptor (EPOR) binds JAK2 as an inactive dimer. In cells with
wild-type JAK2 protein, the binding of erythropoietin (Epo) to its
receptor induces conformational changes in the receptor, resulting
in phosphorylation (P) of JAK2 and the cytoplasmic tail of the
receptor. This leads to signaling through pathways made up of Janus
kinases and signal transducers and activators of transcription
(JAKSTAT), phosphatidylinositol 3 kinase (PI3K), and RAS and
mitogen-activated protein kinase (RASMAPK). In cells with the V617F
mutation, the signaling is constitutively increased, even in the
absence of erythropoietin. In Panel B, the JAK2 protein binds to
multiple cytokine receptors EPOR, thrombopoietin receptor (MPL),
granulocyte colony-stimulating factor receptor (G-CSFR), and
probably others that are important for hematopoietic stem-cell
biology and differentiation. Therefore, the JAK2 protein with the
V617F mutation exerts its effects at various stages of
differentiation and in various lineages. In Panel C, the
development of homozygosity for the V617F mutation is a two-step
process, with the initial point mutation followed by mitotic
recombination of chromosome 9p between the JAK2 locus and the
centromere. This results in the loss of heterozygosity but a
diploid DNA copy number. NEJM 2006; 355:2452
Slide 7
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Polycythemia vera Elevated RBC mass, typically high platelets
and WBC Some patients present with thrombocytosis and develop
erythrocytosis subsequently Hypercellular marrow with variable
degree of reticulin fibrosis Morphology fairly normal, some
clustering and dysmorphism of megas Splenomegaly in 70%,
constitutional sx, increased risk of arterial & venous
thrombosis (esp portal vein), microvascular disease
(erythromelalgia, pruritus, headache, etc), hypermetabolic sx &
gout
Slide 10
Differential diagnosis of erythrocytosis H&P COPD or other
possible causes of hypoxemia? Smoker? Splenomegaly, pruritus,
erythromelalgia? Concomitant thrombocytosis and/or leukocytosis?
Serum EPO JAK-2 mutation testing
Slide 11
Polycythemia Vera Natural History Life expectancy decreased (3
deaths/100 pts/yr) Cardiovascular mortality increased 1.4x Major
thrombosis in 3/100pts/yr Risk of death from leukemia increased 36-
fold Progressive myelofibrosis
Slide 12
NEJM 2004; 350:99
Slide 13
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Oxygen delivery vs Hematocrit J Clin Invest 1963;42:1150
Slide 15
Vaso-occlusion in P vera
Slide 16
Thrombosis in myeloproliferative disorders 41% of deaths in PV
from cardiovascular causes 15% coronary dz 8% CHF 8% non
hemorrhagic stroke 8% PE Complex pathophysiology Abnormal
RBC/WBC/plt function Activated PMNs/cytokines affect vascular
endothelium Prothrombotic microparticle release Increased whole
blood viscosity
Slide 17
Risk factors for thrombosis in myeloproliferative disorders Hx
of thrombosis Disease category (PV > ET, MF) Cardiovascular risk
factors (lipids, blood pressure, smoking, diabetes) Age OCP therapy
(splanchnic vein clots) JAK2 mutation status/allele burden High
hematocrit (PV) & WBC Extreme thrombocytosis increases bleeding
risk Thrombophilic genetic traits?
Slide 18
Prothrombotic effects of erythrocytosis Barbui et al. Blood
2013;122:2176-2184
Slide 19
Hematology 2005:201
Slide 20
Recommendations for treatment of patients with polycythemia
vera Keep Hct < 45 (plebotomy) Low dose ASA unless
contraindicated Manage reversible risk factors (BP, lipids,
smoking) Consider cytoreduction if: Intolerant to phlebotomy
Thrombocytosis or substantial leukocytosis Symptomatic splenomegaly
Choice of cytoreductive therapy: Age < 40: Interferon-alpha Age
> 40: hydroxyurea Anagrelide or busulfan for patients intolerant
of, or not responsive to, above choices
Slide 21
Slide 22
Aspirin vs placebo in P vera
Slide 23
Essential thrombocytosis Thrombocytosis (typically > 600K)
with variable leukocytosis, normal RBC count About 50% have JAK2
mutation Normal to mildly hypercellular marrow with marked increase
in megakaryocytes, often with clustering Minimal reticulin fibrosis
Splenomegaly in about 50% Many patients asymptomatic at diagnosis
Increased risk of arterial and venous thrombosis as well as
hemorrhage
Slide 24
Thrombocytosis Differential diagnosis Essential thrombocythemia
Other MPD P vera Myelofibrosis CML Myelodysplasia (5q- et al)
Reactive Inflammation Surgery/trauma Non-myeloid malignancy Iron
deficiency Hemolysis Acute blood loss Absence of spleen Rebound
following thrombocytopenia
Slide 25
Hematology 2005:201
Slide 26
Essential Thrombocytosis Natural History 1-2 cases/100,000/yr
Most patients >50, but occurs in young adults Woman more often
affected than men Life expectancy normal to slightly decreased
Patients > 60, or with prior thrombosis, at increased risk for
thrombotic events Very high platelet counts (>1.5 million)
increase risk of bleeding, not thrombosis Risk of myelofibrosis
about 8% at 10 years Risk of AML about 1% overall
Slide 27
Essential Thrombocytosis Treatment Low-risk patients (young, no
vascular risk factors) may not require treatment Aspirin decreases
thrombotic events Hydroxyurea Anagrelide Interferon Other: busulfan
(leukemogenic)
Slide 28
Hematology 2005:201 Recommendations for treatment of patients
with essential thrombocytosis Manage reversible risk factors (BP,
lipids, smoking) If hx of thrombosis, or age >60, or plts >
1.5 million: Hydroxyurea Low dose ASA unless for plts > 1.5 m 2
nd line: Anagrelide or interferon-alpha Age < 60, no other risk
factors: Low dose ASA
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Myelofibrosis 0.5-1.5 cases/100,000/yr Most patients >60
Marrow fibrosis with extramedullary hematopoiesis in spleen, liver,
many other tissues Prefibrotic stage with hypercellular marrow
& abnormal megakaryocytes Peripheral leukoerythroblastosis,
teardrop cells, often with anemia. WBC and platelet counts may be
high, normal or low Splenomegaly, constitutional symptoms Poor
prognosis: marrow failure, AML in 5-30%
Slide 31
Improving survival in MF Median survival 6.5 yrs Median
survival 4.5 yrs J Clin Oncol 2012;30:2981
Slide 32
DDx of Marrow Fibrosis DDx of Marrow Fibrosis
Myeloproliferative disorders MF > > P vera, ET, CML Other
heme neoplasm Megakaryocytic leukemia Hodgkins Hairy cell leukemia
Non-heme cancer Non-malignant conditions Renal osteodystrophy
Autoimmune disease Vitamin D deficiency
Slide 33
SPLENOMEGALY IN MYELOFIBROSIS Mayo Clin Proc 2004;79:503
Slide 34
Myelofibrosis Treatment Supportive care Transfusions
Splenectomy Thalidomide/lenalidomide (low dose) Reduce transfusion
requirements, reduce spleen size Chemotherapy (limited data;
myelosuppression often dose-limiting) Cladribine
Azacytidine/decitabine Low dose cytarabine Marrow transplant in
selected patients JAK inhibitor therapy: Ruxolitinib (inhibits
JAK-1 and JAK-2)
Clonal eosinophilic disorders caused by mutations in tyrosine
kinase genes PDGFRA, PDGFRB May be cytogenetically silent FISH
testing for dx Marrow fibrosis, incr mast cells, elevated tryptase
variant of mast cell dz? Male predominance Imatinib-responsive
(100-400 mg/d) FGFR1 Associated with 8p11 translocations Stem cell
disorder aggressive MPD associated with T-lymphoblastic lymphoma
High dose chemotherapy + allo-HSCT
Slide 42
Chronic eosinophilic leukemia WHO diagnostic criteria
Eosinophil count > 1500 No Ph chromosome or BCR-ABL fusion No
PDGFRB, PDGFRA or FGFR1 rearrangement Blast count in blood and
marrow < 20% No inv (16) or other variant characteristic of AML
Presence of clonal cytogenetic or molecular abnormality OR blasts
>2% in blood or >5% in marrow
Slide 43
Idiopathic Hypereosinophilic Syndrome
Slide 44
Laboratory evaluation of hypereosinophilia Marrow biopsy with
cytogenetics FISH for PDGFR mutations Serum tryptase T-cell
immunophenotyping and gene rearrangement study Serum IL-5 Serum IgE
Screen for organ damage Echo, troponin level CXR, PFTs
Slide 45
Classification of Mast Cell Disease WHO classification and
frequency in Mayo Clinic series Indolent often limited to skin
(urticaria pigmentosa (46%) Associated with myeloproliferative
disorder (40%) Aggressive mastocytosis with lymphadenopathy &
eosinophilia (12%) Mast cell leukemia (1%) Blood 2009;113:5727
Slide 46
WHO Diagnostic Criteria for Mast Cell Disease Major: multifocal
dense infiltrates of mast cells (15+) in marrow or other
extracutaneous organs Minor >25% spindle shaped or otherwise
atypical MC c-KIT codon 816 mutation MC in marrow or other
extracutaneous organ express CD2 and/or CD25 Serum tryptase
persistently >20 ng/ml in the absence of another clonal myeloid
disorder Diagnosis requires major + 1 minor criterion or at least 3
minor criteria
Slide 47
Stuff in mast cell granules that could make you sick Metcalfe,
Blood 2008;112:946
Slide 48
Clinical & laboratory features of mast cell disease Skin:
Urticaria pigmentosa, Darier sign (dermatographism),
telangiectasias Lymphadenopathy Hepatosplenomegaly Constitutional
symptoms Recurrent anaphylaxis GI symptoms (N/V, diarrhea, abd
pain, peptic ulcer) Elevated serum/urinary histamine levels
Elevated serum tryptase (96%) Cytopenias Eosinophilia Coagulopathy
(heparin in mast cells) rare Lytic or blastic bone lesions
Molecular biology of mast cell disease A majority of patients
have D816V mutation in c-KIT tyrosine kinase gene
(imatinib-insensitive) A minority have other mutations, may be
imatinib-sensitive Occasionally found together with JAK2 V617F Some
patients have eosinophilia & PDGFRA mutation
(imatinib-responsive)
Slide 54
Treatment of mast cell disease Antihistamines, PPIs Vit
D/Calcium, bisphosphonates Glucocorticoids Epinephrine (for
anaphyactic reactions) For aggressive disease: Interferon Imatinib
(if there is an imatinib-sensitive mutation) Other TKIs (dasatinib,
nilotinib)? Cladribine Combination chemotheapy Allo-HSCT
Slide 55
Survival of patients with MCD Blood 2009; 113: 5727