Myeloproliferative neoplasms (MPN)

Myeloproliferative neoplasms (MPN)
a group of closely related clonal disorders of haemopoiesis that lead to an increase in
the numbers of one or more mature blood cell progeny. Those disorders share common
features and they have the possibility to transform from one to another and all of them
have the potential to evolve into acute leukemia with a variable frequency (it is more
common in chronic myeloid leukemia than the other disorders).
classically it includes 4 closely related disorders:1- CML (Philadelphia positive CML)
2- polycythemia rubra vera.
3- Essential thrombosythenia .
4- Primary Myelofibrosis.
Other disorders have also been included but they are less common including ;1- Chronic neutrophilic leukemia.
2- Chronic eosinophilic leukemia.
3- Systemic mastocytosis.
4- Myeloproliferative disorders unclassifiable.
In MPN there is often a mutation in a gene encoding a protein on a signaling pathway
between the surface membrane and the nucleus; often this protein is a tyrosine kinase
that becomes constitutively activated as a result of the mutation. The neoplastic cells
are thus able to proliferate and differentiate without being dependent on growth factors.
Philadelphia +ve chronic myeloid leukemia:Clonal disorder of pluripotential stem cells , the stem cells proliferate & generate a
population of differentiated cells that gradually replace normal hemopoietic cells , it is
classified as one of the myeloproliferative diseases. it accounts for 15% of leukemia &
the median age of onset is 40- 50 years, ♂>♀. The only known risk factor is exposure
to ionizing radiation.
Cytogenetics:Philadelphia chromosome (Ph) is found in nearly 90-95% of cases of CML. It is found
in all myeloid cells , some B lymphocytes & very small proportion of T cells & in no
other cells in the body.
(Ph) chromosome results from t(9;22) (q34;q11), as a result the ABL proto-oncogene is
removed from chromosome 9 to 22& part of the BCR gene on chromosome 22 is
moved to 9 .
Ph chromosome is the abnormal shortened chromosome 22 where the 5 exon of the
BCR gene is fused to the 3 exon of the ABL gene , the resultant gene codes for fusion
protein (210 kda) with excess tyrosine kinase activity than the normal 140 kda protein.
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Ph chromosome may be seen in ALL here the break point in the ABL gene is the same
however the break in the BCR gene is further up, resulting a chimeric gene coding for a
(190 kda) protein which also has increased tyrosine kinase activity.
In a minority of patients the Ph chromosome abnormality can not be detected by
karyotyping but requires more sensitive molecular techniques , this form of BCR-ABL
+ve Ph –ve CML behaves like Ph+ve CML.
Additional clonal cytogenetic abnormalities are acquired during the disease course as
+ 8 ,+19 , iso -17q , this means usually that the new clone will expand & that blastic
transformation will manifest itself with in weeks or months .
Disease course :CML is a biphasic or triphasic disease that is usually diagnosed in the chronic phase ,
the chronic phase usually last for about 2-7 years occasionally 10-15 year , in 30% of
patients the chronic phase transform abruptly to to blastic phase (blastic crises ), more
commonly the disease progress gradually to accelerated phase which may last for
months or sometimes years before blastic transformation with anemia , ↓platelet ,↑
basophil & eosinophil & blasts in the blood .
In about 1/5 of cases of blastic transformation is lymphoblastic but in the majority the
transformation is to AML.
Clinical features:1- in about 30-50% of cases the diagnosis is incidental by performing routine
blood count .
2- patients usually presented with symptoms related to hypermetabolisim (weight
loss , anorexia, night sweat).
3- Spleenomegally is nearly always present & frequently massive associated with
discomfort.
4- Features of anemia , bleeding manifestations .
5- Renal impairment & gouty arthritis caused by ↑uric acid .
Investigations:1- Blood picture reveals leukocytosis usually >50 ×109 /L with a complete
spectrum of myeloid cells with 2 peaks of neutrophils & myelocytes .
2- increase basophils in blood .
3- platelet count is frequently ↑, or may be normal or ↓.
4- NAP score is low, helpful to differentiate it from infection & from other MPD
where it is increased...
5- Bone marrow study shows a hyper cellular marrow with predominance of
granulocytic component (M/E ratio is increased to 12/1)
6- Ph chromosome can be demonstrated by cytogenetic analysis.
7- Uric acid usually ↑ as well as B12 & B12 binding capacity.
Keep in mind that CML may be diagnosed based on peripheral blood findings and
cytogenetic study without the need for bone marrow study.
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Criteria for diagnosis of chronic accelerated and blastic phases of CML
Treatment:
Previously CML patients were treated with hydroxyurea, busulphan and α interferon or
when possible with bone marrow transplantation now with the development of
imatinib, a tyrosine kinase inhibitor that is active against the BCR-ABL fusion gene
products the treatment has greatly changed and now it is the first line of treatment, it is
given orally, less toxic and can produce hematological remission as well as cytogenetic
and molecular remission.
Philadelphia negative myeloproliferative neoplasms:The recent observation that patients with myeloproliferative disorders (excluding CML)
frequently have a mutation on the short arm of chromosome 9, in which the valine at
position 617 of the Janus kinase 2 gene is replaced by phenylalanine (JAK2 V617F)
This mutation appears to be present in up to 95% of PV patients at diagnosis and about
half of patients with essential thrombocythemia and myelofibrosis.
The JAK 2 is a protein kinase associated with the haemopoietic growth factor receptor.
The mutation allows the JAK 2 protein to become activated even when no growth
factor is bound to the receptor and this leads to cell survival and proliferation .this
mutation is detected in granulocytes and also B lymphocytes and a small proportion of
T cells. However it is still not clear why the same mutation give us different disorders?
Polycythemia rubra vera.:is a myelo - proliferative neoplasm (MPN) in which the total volume of red cells in the
circulation is increased as a result of mutation of a multipotent haemopoietic stem cell.
& in many patients there is also increase in production of granulocytes & platelets.
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It is a disorder of middle aged and old people. the clinical features results from hyper
viscosity & hypervolumia & hypermetabolisim.(head ache , dyspnea , blurred vision,
pruritis, plethoric appearance , spleenomegaly , hemorrhage or thrombosis(arterial or
venous)
Polycythemia can be - absolute with a true increase in red cell mass
- Relative with a decrease in plasma volume
Absolute polycythemia may be - primary (rubra vera)
- Secondary
Secondary polycythemia could be
1- associated with appropriate increase of Erythropoietin (hypoxic state)as in
-high altitude
-pulmonary diseases with hypoventilation
-cardiovascular diseases especially congenital with cyanosis
-Hb with high affinity to oxygen
-heavy cigarette smoking
2- Associated with inappropriate increase in Erythropoietin as in
- Renal diseases (hydronephrosis, tumors, cysts)
- Tumors as uterine fibromyoma , hepatocellular carcinoma ,
cerebellar haemangioblastoma.
Molecular genetic abnormality:A characteristic molecular abnormality, a V617F mutation in exon 14 of the JAK2
gene, was reported almost simultaneously by a number of research groups and is
observed in about 95% of patients.
The mutation occurs in a pluripotent lymphoid-myeloid stem cell and thus both T and B
lymphocytes can carry the mutation. Although the JAK2 V617F mutation is becoming
increasingly important in the diagnosis of polycythaemia vera it is not specific for this
condition. It is also seen not infrequently (around 50% of cases) in essential
thrombocythaemia, primary myelofibrosi
Criteria for diagnosis:- the WHO criteria for diagnosing polycythemia include
Major criteria:A1- Hb >18.5 g/dl male/16.5 g/dl female; or other evidence of increased RCM
A2. - Presence of JAK2 V617F or other functionally similar mutation
Minor Criteria:B1- Marrow morphology
B2. - Serum erythropoletin below reference range for normal
B3- EEC colony formation in vitro. (EEC, endogenous erythroid colony formation)
Marrow morphology: Hypercellular marrow with trilineage hyperplasia; clustering
of pleomorphic megakaryocytes; absent stainable iron; no major inflammatory
features.
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Diagnosis requires A1 and A2 and any one from B, or A1 and any 2 from B.
Course & prognosis
:Good prognosis, thrombosis & hemorrhage are the 2 main problems (due to ↑
platelet level & hyper viscosity), hemorrhage may be due to defective platelet
function.
30% of patients transform to myelofibrosis
5% of patients transform to acute leukemia
Essential thrombocythmia:Here there is sustained increase in platelet count because of Meqakaryocytes
proliferation & over production of platelets.
Diagnosis is made when there is persistent increase in platelet count >600×10/L
with exclusion of other causes of secondary thrombocytosis (hemorrhage, trauma,
postoperation, chronic iron deficiency, chronic infections , connective tissue
diseases , post spleenectomy), also increase in other MPD .
The dominant clinical features are thrombosis & hemorrhage, 40% of patients have
palpable spleen, and some patients have spleenic atrophy due to infarction,
The blood film may show abnormal large platelets, the bone marrow may show
excess of abnormal Megakaryocytes
Platelet function tests sre always abnormal
The disease may transform after years to myelofibrosis with less than 5% risk of
transforming to acute leukemia.
myelofibrosis :In myelofibrosis there is progressive fibrosis in the bone marrow associated with
the development of extramedullary hemopoiesis in the spleen & liver (myeloid
metaplasia), this leads to anemia & massive hepatospleenomegaly .
The fibrosis is secondary to hyperplasia of abnormal Megakaryocytic & platelets
derived growth factor secreted by them that stimulate fibroblast proliferation. For
example, transforming growth factor-beta (TGF- β) is a glycoprotein that is
produced and released by endothelial cells, monocytes, and megakaryocytes. TGF- β
enhances the production and release of extracellular matrix protein, such as collagen
from fibroblasts
Symptoms are mainly due to massive spleenomegaly , hypermetabolic symptoms
(weight loss , anorexia, fever, night sweat)
Laboratory findings:1- Anemia usually found, the WBC & platelets may be increased at start (hyper
cellular phase) then they decrease, there is leukoerythroblastic blood picture in
the blood film with a characteristic tear drop poikiloocytosis of the RBC.
2- bone marrow aspiration is not usually obtained (dry tab) & biopsy is necessary ,
it will show hyper cellular fibrotic marrow with increase in Meqakaryocytes , in
10% of cases there is increase in bone density on X-ray (bone transformation,
osteomyelosclerosis).
3- Decrease in RBC folate ,↑serum B12 ,↑NAP score , ↑urate &LDH (serum LDH
is normal in PRV )
Transformation to AML occurs in 10-20% of cases.
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Myelodysplatic syndromes (MDS):A heterogenous group of clonal diseases of haemopoietic cells characterized by
peripheral blood cytopenia with a hyper cellular dysplastic bone marrow and an
increased risk of leukemic transformation. in myelodysplastic syndroms maturation is
abnormal (dysplastic) and production is ineffective, resulting in many cells being
destroyed before they reach the systemic circulation. Dysplasia may involve one or
more hematopoietic lines; to be significant it should affect at least 10% of that line's
cells in the bone marrow.
The WHO classification of MDS classify those disorders into the following groups:
1-refractory cytopenia with unilinage dysplasia (RCUD):- there is only one line
involved ,other cells are not involved and the marrow shows dysplasia confined to that
line only only (refractory means cytopenia persisting for at least 6 months with no
identifiable cause and no response to treatment).
2- Refractory anemia with ring sideroblasts (RARS):- the same as refractory anemia but
there is also ≥ 15% ring sideroblast in the bone marrow iron stain.
3- Refractory cytopenia with multilinage dysplasia with or without ring sideroblasts
(RCMD±RS):-charecterized by peripheral cytopenia with bone marrow dysplasia
involving more than one line but still the blast percentage is less than 5% , ring
sideroblasts may be present or absent.
4- Refractory anemia with excess blasts 1 (RAEB 1):- dysplsia in more than one line
with blasts ranging from 5-9% in the bone marrow.
5- Refractory anemia with excess blasts 2 (RAEB 2):- dysplsia in more than one line
with blasts ranging from 10-19% in the bone marrow.
6- myelodysplastic syndroms unclassifiable :- the features does not fit in any other
category.
7- myelodysplastic syndroms associated with isolated 5q- syndrome .
Overall the incidence of MDS is about three times that of AML and rises exponentially
with age. The incidence in men is about twice that in women A number of aetiological
factors are known, including irradiation, exposure to anti-cancer chemotherapy
(particularly alkylating agents) benzene and cigarette smoking. There are also genetic
disorders that predispose to MDS; these include Diamond–Blackfan anaemia, Fanconi
anaemia,
Initial investigation of patients with suspected MDS should include full blood count,
differential count, reticulocyte count and blood film, bone marrow aspirate including
iron stain and cytogenetic analysis. Consideration should be given to the need for
testing for human immunodeficiency virus (HIV) infection and for assaying serum
vitamin B12, and folate.
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Chronic lymphoid leukemia
Include several disorders characterized by proliferation of mature looking lymphocytes
of either Tor B lines.
In about 98% of patients the disease is of B lineage, there is overlap with lymphoma
In lymphoma (NHL) the diseases is present in soft tissues while in chronic lymphoid
leukemia it is present in blood & bone marrow.
Chronic lymphocytic leukemia:The most common of the chronic lymphoid leukemias , the cells are mature B cells
with weak expression of surface IgM ,IgD , they accumulate in the bone marrow,
blood, liver, spleen, LN as a result of prolonged life span & impairment of apoptosis.,
the etiology is unknown.
Clinical features:Seen in old people usually more than 50 year, ♂: ♀ 2:1.
50%of cases diagnosed incidentally (routine check up).
The most frequent sign is symmetrical enlargement of superficial LN; the nodes are
discrete, non tender.
Spleenomegally &hepatomegally usually seen later on .
Anemia & infection (due to immune deficiency & neutropenia) are usually seen later on
in the disease.
Purpura when there is thrombocytopenia.
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Laboratory findings:The diagnosis requires persistent lymphocytosis >10 × 10 9/ L with bone marrow
infiltration of at least 40% , however with immunological methods in the presence of
evidence of monoclonal B cell proliferation it is possible to diagnose CLL with less
counts. The cells are mature looking lymphocytes, smudge cells may be seen, some
prolymphocytes nearly always present .
.
Anemia or thrombocytopenia usually seen late in the disease course however
autoimmune hemolytic anemia may occur in 8% of patients, also nutritional anemia
may complicate the condition.
Some patients have +ve coombs test without overt hemolysis.
-bone marrow aspiration shows lymphocytes replacement of the normal haemopoietic
elements , the bone marrow biopsy shows the pattern of involvement which could be
nodular, diffuse, interstitial, or mixed.
-immunophenotyping show a combination of surface markers that are characteristic
Marker
score
SM Ig(weak)
1
CD 5+
1
CD 23 +
1
FMC 7 (-)
1
CD 79b (-)
1
Total
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CLL scores 4-5 while other B cell lymphoproliferative diseases score 0-1 or even 2 but
not more.
-decrease serum Ig.
- Chromosomal abnormalities detected are
Deletion of 13q14
Trisomy 12
Deletion of 11q23
Structural abnormalities of chromosome 17 involving P53 gene.
Usually these changes are associated with disease progression & poor prognosis.
Staging system:Staging is useful for both prognosis & making therapy decisions, 2 systems for staging
Rai classification & the Binet etal staging.
Binet et al staging classify the disease into 3 stages
Stage A:- absolute lymphocytosis and not more than 2 regions of lymph node enlarged
(ex axillary and cervical ), hemoglobin greater than 10gm/dl and platelets greater than
100× 109/l.
Stage B:- absolute lymphocytosis with more than 2 regions of lymph nodes enlarged,
hemoglobin greater than 10gm/dl and platelets greater than 100× 109/l.
Stage C:- hemoglobin concentration less than 10 and platelet count less than 100
regardless to the number of lymph regions involved.
Note;- a region being cervical, axillary ,inguinal, liver ,spleen regardless weather the
lymph nodes are unilateral or bilateral
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Anemia and thrombocytopenia should be due to the disease progression (i.e. not due to
nutritional or immunological bases)
Rai staging system classify the disease into 5 stages;Stage0:- absolute lymphocytosis more than 15× 109/l
Stage I:- as stage 0 with enlarged lymph nodes (adenopathy).
Stage II:- as stage 0 + enlarged liver or spleen ± adenopathy .
Stage III:- as stage 0 + anemia (Hb less thsn 10 g/dl) ± adenopathy ± organomegally.
Stage IV:- as stage 0 + thrombocytopenia (platelets less than 100×109/l) ± adenopathy±
organomegally.
Course of the disease:Many patients do not need treatment (Rai stage 0 or I Binet stage A).
The disease may transform into
1- Richters transformation, localized high grade NHL.
2- Prolymphocytic leukemia with increase in the number of prolymphocytes in the
blood > 50%.
Prolymphocytic leukemia:May appear initially as B-CLL with increase in percentage of prolymphocytes in blood
the prolymphocytes are characterized by their shape they are about twice the size of
lymphocyte, low N/C ratio, eccentric nucleus, moderately condensed chromatin with a
large central nucleolus.
B cell prolymphocytic leukemia is 3 times more common than T cell prolymphocytic
leukemia.
Clinically they are presented with splenomegally with out lymphadenopathy .
the WBC count is high & rapidly increasing ,cells are FMC7 +ve &also for surface
membrane Ig is strongly expressed .
This form of leukemia is difficult to treat
Hairy cell leukemia:B cell lymphoproliferative disease with peak incidence at 40-60 years , male: female
ratio 4:1 , patients presented with symptoms of anemia , infection due to leucopenia ,
huge spleenomegally , lymphadenopathy is very uncommon.
Usually patients have pancytopenia at presentation & the blood film reveals hairy cells
(large lymphocytes with villous cytoplasmic projections, smooth chromatin with
absence of visible nucleoli.
Immunophenotyping show characteristic CD22, FMC7, CD103 +ve.
Bone marrow aspirate is usually unsuccessful therefore a biopsy is essential , it will
show loose infiltrate leaving plenty of space between cells with a clear zone around
each cell (fried egg appearance) , there is also mild fibrosis .
By cytochemistry TRAP (tartarate resistant acid phosphatase )is +ve.
Hairy cell leukemia variant:Very rare characterized by high WBC count, hairy cells have prominent nucleoli, it
respond less to treatment.
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Paroproteinemia :the presence of a monoclonal Ig band in the serum (normally Ig are polyclonal), this
monoclonal band reflects the synthesis of Ig from a single plasma cell clone.
Multiple myeloma:Neoplastic proliferation of plasma cells in the bone marrow characterized by lytic bone
lesions, plasma cell accumulation in the bone marrow & the presence of monoclonal
protein in the serum & urine.
The etiology is unknown but cytokines have important role (IL-6 is an important
growth factor for myeloma cells, also the osteolytic lesions result from TNF &IL that
stimulate osteoclasts , those cytokines are secreted by myeloma cells.
Structural chromosomal abnormalities have also been detected.
Clinical features:1- Bone pain (especially back pain) & pathological fracture.
2- Features of anemia
3- Recurrent infection due to decrease in Ab production & neutropenia
4- Features of renal failure & hypercalcemia
5- Increase bleeding tendency as the Para protein may interfere with platelet &
coagulation factors function.
Diagnosis:Depend on 3 principle findings
1- Monoclonal protein in the serum or urine (or both), in 2/3of cases it is IgG,
rarely IgM o r IgD or mixed.
Normal serum Ig are reduced
In 2/3 of cases the urine contains Bence-Jones protein (free light chain of Ig
either κ or λ, of the same type as the para protein).
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In 15% of cases Bence-Jones is +ve with out serum Para protein , rarely
myeloma is not associated with para protein (called non- secretory myeloma).
2- increase plasma cells in the bone marrow more than 20% with abnormal forms .
3- osteolytic bone lesions without surrounding sclerosis or osteoblastic reaction ,
sometimes there is generalized osteoparosis & in 20% of cases there is no bone
lesions at all.
2 of the 3 features should be present to make the dignosis.
Other laboratory features include
1- anemia, high ESR , increase rouleaux
formation , neutropenia &
thrombocytopenia in advanced disease .
2- Serum calcium is increased with a normal alkaline phosphatase (except when
there is fracture). Urea & creatinine are also increased & in advanced disease
albumin is also reduced.
3- Serum B2-microglobulin is increased & it is a useful indicator of prognosis (if
low good prognosis).
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