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MEH > 5.2 When haemopoiesis goes wrong > Flashcards

5.2 When haemopoiesis goes wrong Flashcards

1
Q

what can cause overproduction of cells in haemopoiesis?

A
  1. myeloproliferative disorders.

2. physiological reaction

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2
Q

Give examples of common myeloproliferative disorders/myeloproliferative neoplasms?

A

essential thrombocythaemia
polycythemia vera
myelofibrosis
chronic myeloid leukaemia

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3
Q

what are clinical features of myeloproliferative disorders?

A 
overproduction of one or several blood elements with dominance of a transformed clone.  
hypercellular marrow
cryogenic abnormalities 
thrombotic and haemorrhage diathesis 
extra medullary haemopoiesis
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4
Q

what genetic mutation do many patients with myeloporliferative disorders have?

A

a single point mutation in one copy of the Janus kinase 2 gene (JAK2)

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5
Q

how does a mutation of the Janus kinase 2 gene cause overproduction of cells?

A

causes increased proliferation and survival of haematopoietic precursors.

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6
Q

what is the diganostic criteria for patients with suspected polycythemia vera?

A

high haematocrit
no reactive cause found.
high platelets and neutrophils

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7
Q

who is typically affected by polycythemia vera?

A

median age of 60

males and females are equally affected.

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8
Q

what is pruritis?

A

itchiness

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9
Q

what are clinical features of polycythemia vera?

A 
pruritis 
venous thrombosis
arterial thrombosis (heart attacks)
haemorrhage into the skin or GI tract
splenic discomfort / splenomegaly
gout
transformation to myelofibrosis or acute leukaemia
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10
Q

how are patients with polycythaemia vera managed?

A

venesection to maintain a lower haematocrit level
aspirin
manage CVS risks factors.
sometimes drugs to manage the overproduction of cells (hydroxycarbamide)

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11
Q

what is polycythaemia?

A

an increase in circulating red cell concentration. Observed by a persistently raised haematocrit

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12
Q

what is the difference between relative and absolute polycythemia?

A 
relative = normal red cell mass with decreased plasma levels 
absolute = increased red cell mass
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13
Q

what is a primary cause of polycythaemia?

A

polycythaemia vera

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14
Q

what is a secondary cause of polycythaemia?

A

production driven by increased erythropoietin production (may be appropriate or inappropriate)

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15
Q

when is central hypoxia experienced?

A

chronic lung disease (COPD)
right to left shunts
training at altitude
co poisoning

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16
Q

what can cause renal hypoxia?

A

renal artery stenosis

polycystic disease

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17
Q

Give an example of physiologically appropriate erythropoietin production

A

living in high altitude (oxygen sats are lower)

chronic lung disease

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18
Q

give an example where there is abnormal increased production of erythropoietin

A

renal carcinoma
renal artery stenosis
(erythropoietin usually produced in the kidneys)

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19
Q

what is essential thrombocythaemia?

A

excess platelets in the blood. large excess megakaryocytes in the bone marrow

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20
Q

how is essential thrombocythaemia managed?

A

cardiovascular risks managed
aspirin
return platelet count to normal with drug such as hydroxycarbomide

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21
Q

what should first be done after noting a high platelet count?

A

decide whether the increase in platelets is transient or persistent. To do this we must look for any reactive causes such as infection, inflammation, tissue injury, haemorrhage, cancer or redistribution of platelets ( post-splenectomy and hyposplenism)

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22
Q

what is myelofibrosis?

A

Myelofibrosis is a rare disease of the bone marrow in which collagen builds up fibrous scar tissue inside the marrow cavity. This is caused by the uncontrolled growth of a blood cell precursor (haemopoietic stem cell), which results in the accumulation of scar tissue in bone marrow.

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23
Q

how does myelofibrosis affect haematopoiesis?

A

as the central area of callous bones ossified to cortical bone, leaving little space for haemopoiesis. This results in splenomegaly and hepatomegaly due to extra medullary haematopoiesis.

24
Q

how does cell count vary in primary myelofibrosis?

A

initially the cell counts are all high in the proliferative phase. All cases then progress to pancytopenia due to bone marrow fibrosis and hyperplneism.

25
Q

what are the clinical features of myelofibrosis?

A

fatigue, sweats
consequences of massive splenomegaly ( pain, early satiety, splenic infarction)
problems associated with transfusions of blood product ( iron overload)
transformation to leukaemia
early death

26
Q

what is chronic myeloid leukaemia?

A

An indolent leukaemia, characterised by increased mature granulocytes in the peripheral circulation.

27
Q

what are the clinical presentations of a patient with chronic myeloid leukaemia?

A

Often asymptomatic; commonly present with splenomegaly, hyperviscosity(resulting in headaches and SOB) or bone pain. may present with left sided pain, general malaise, joint pain, low-grade fever, pancytopaenia resulting in increased infections, anaemia, thrombocytopaenia.

28
Q

what group of people are more likely to suffer from chronic myeloid leukaemia?

A

Adults, very rare in children.

29
Q

what will a blood film of a patient with chronic myeloid leukaemia show?

A

blood film will show lots of myelocytes spilling into the peripheral blood that should be in bone marrow. Blood film and marrow will show excess of all myeloid series from blast through to fully mature neutrophils

30
Q

what is the Philadelphia chromosome?

A

An abnormally shortened chromosome 22, formed by translocation of a portion of the long arm of chromosome 22 to chromosome 9; found in cultured leukocytes of many patients with chronic myeloid leukemia. This rearranged chromosome 22 causes abnormal activity of a form of tyrosine kinase.

31
Q

what affect does a Philadelphia chromosome have on proliferation of leukocytes?

A

philadelphia cell switches on a receptor for tyrosine kinase which drives proliferation of leukocytes.

32
Q

what genes are fused on chromosome 22 during chronic myeloid leukaemia?

A

after a section of the long arm of chromosome 9 has been translocated to the long arm of chromosome 22, the BCR gene of chromosome 22 and the all gene of chromosome 9 fuse. This BCR-abl fusion is present in Philadelphia chromosomes.

33
Q

how is chronic myeloid leukaemia treated?

A

Treated with tyrosine kinase inhibitors such as imatinib. This binds to the BRC-abl protein and inhibits the substrate from binding. Tumour ell therefore can no longer proliferate. Very successful treatment.

34
Q

what is pancytopenia?

A

reduction in all blood cell types ( white cells, red cells and platelets)

35
Q

what 2 methods can pancytopenia be caused by?

A 
reduced production (most common)
or increased removal
36
Q

what conditions cause increased removal of blood cells resulting in pancytopenia?

A
  1. immune destruction
  2. splenic pooling (splenomegaly)
  3. haemophagocytosis (blood cells chewed up in bone marrow)
37
Q

what conditions can lead to reduced production of blood cells?

A 
B12/Folate deficiency
bone marrow infiltration by malignancy 
marrow fibrosis
bone marrow exposed to ionising radiation
drugs (chemotherapy, antibiotics, anticonvulsants)
viruses (EBV, viral hepatitis, HIV, CMV)
idiopathic aplastic anaemia
congenital bone marrow anaemia
38
Q

what does congenital mean?

A

existing at birth

39
Q

what is aplastic anaemia?

A

Aplastic anemia is an autoimmune disease in which the body fails to produce blood cells in sufficient numbers. Blood cells are produced in the bone marrow by stem cells that reside there. Aplastic anaemia causes a deficiency of all blood cell types: red blood cells, white blood cells, and platelets.

40
Q

what are the defining features of aplastic anaemia?

A
  • pancytopenia
  • hypo cellular bone marrow in the absence of an abnormal infiltrate
  • no increase in reticulin ( fibrosis)
41
Q

what are the risks associated with aplastic anaemia?

A

high risk of infection due to pancytopenia

high mortality rate (deaths often due to neutropenic infection or bleeding

42
Q

how is aplastic anaemia treated?

A

immune treatments

bone marrow transplants

43
Q

what is the role of platelets?

A

facilitate clot formation, initially via a platelet plug

44
Q

how do platelets form a ‘plug’?

A
  1. Adhesion ( to damaged endothelial wall and to von Willebrand factor vWF)
  2. Activation (change in shape from disc to release granules )
  3. Aggregation (clumping together of more platelets to form the plug)
45
Q

what is a quantitative platelet disorder?

A

low platelet count ( thrombocytopenia)

46
Q

what is a qualitative platelet disorder?

A

often a normal number of platelets but a defective function

47
Q

how can thrombocytopenia by acquired?

A

decreased platelet production
increased platelet consumption
increased platelet destruction

48
Q

what conditions may lead to decreased platelet production?

A 
B12/folate deficiency 
acute leukaemia
aplastic anaemia
liver failure (decreased thrombopoietin production)
sepsis
cytotoxic chemotherapy
49
Q

what conditions may cause increased platelet consumption?

A

massive haemorrhage
Disseminated intravascular coagulation
thrombotic thrombocytopenia purpura

50
Q

what conditions may cause increased platelet destruction

A 
autoimmune thrombocytopenic purpura
drug induced (heparin)
hypersplenism resulting in increased destruction and splenic pooling of platelets
51
Q

what are the consequences of severe thrombocytopenia?

A 
easy bruising 
petechiae, purpura
mucosal bleeding
severe bleeding after trauma 
intracranial haemorrhage
52
Q

what are the causes of immune destruction of platelets?

A
  1. immune thrombocytopenic purpura.

2. secondary to immune disease (SLE)

53
Q

how is immune destruction of platelets treated?

A

immunosuppression (corticosteroids or intravenous immunoglobulin first line)

54
Q

what are hereditary disorders of platelet function?

A

Bernard Soulier syndrome

Glanzmann’s thrombasthenia

55
Q

what are acquired disorders of platelet function?

A

Aspirin/NSAIDS
uraemia
myeloma
myeloproliferative disorders

MEH (23 decks)

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