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MEH > Anaemia, Vit B12 > Flashcards

Anaemia, Vit B12 Flashcards

1
Q

Reasons for reduced erythropoiesis

A
  • Lack of response to the haemostatic loop e.g. kidney disease, the kidney stops making erythropoietin
  • Empty bone marrow e.g. aplastic anaemia
  • Marrow infiltrated e.g. cancer or fibrosis tissue
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2
Q

Dyserythropoiesis example

A
  • Anaemia of chronic disease

- Myelodysplastic syndromes

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3
Q

Anaemia of chronic disease: seen in, features

A
  • Inflammatory conditions such as rheumatoid arthritis, inflammatory bowel disease (Crohn’s and Ulcerative Colitis)
  • Chronic infection e.g. TB
  • Iron stored in macrophages not released, red cells have reduced life span, marrow shows lack of response to erythropoietin
  • Anaemia may be microcytic, normocytic or macrocytic
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4
Q

Myelodysplastic syndromes: seen in, features, diagnosis made by, type of anaemia, treatment

A
  • Usually elderly, but can occur earlier
  • Production of abnormal blood cells which are not fully developed (abnormal clones of marrow stem cells)
  • Diagnosis made by microscopy of cells
  • Macrocytic anaemia
  • Red cells are prematurely destroyed
  • Acute leukaemia develops in high proportion of cases
  • Treated by chronic blood transfusions
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5
Q

Haemoglobin abnormalities

A
  • Lack of iron
  • Deficiency in building blocks for DNA synthesis ( Vit B12 and folate)
  • Mutations in genes that encode the globin protein (thalassaemia, sickle cell)
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6
Q

Why is B12 and folate important in red blood cell production?

A
  • Necessary for nuclear divisions and nuclear maturation
  • When deficient, both lag behind cytoplasm development
  • Leads to large red cell precursors, with inappropriately large nuclei and open chromatin
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7
Q

Absorption of B12

A
  • Haptocorrins
  • B12 pairs with the glycoprotein intrinsic factor(IF) produced by parietal cells in stomach
  • IF B12 complex binds in ileum, B12 gets absorbed, IF destroyed
  • In portal blood B12 is bound to the plasma protein transcobalamin, which delivers B12 to the bone marrow and other tissues
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8
Q

Deficiency of B12 could result from:

A
  • Dietary deficiency
  • Pernicious anaemia (affects gastric parietal cells causing lack of intrinsic factor)
  • Disease of the terminal ileum (Crohn’s, IF-B12 unable to bind)
  • Congenital deficiency in transcobalamin
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9
Q

Absorption of folate

A
  • Occurs in the duodenum and jejunum
  • All dietary folates converted to methyltetrahydrofolate (methylTHF)
  • MethylTHF is needed for DNA synthesis
  • Stored in the liver
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10
Q

Deficiency of folate could result from:

A
  • Dietary deficiency or increased use (pregnancy, increased erythropoiesis, severe skin disease)
  • Proximal small bowel disease (Crohn’s and coeliac)
  • Drugs can inhibit dihydrofolate reductase enzume (something to do with methylTHF)
  • Alcoholism, urinary loss of folate in liver disease, heart failure
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11
Q

What can occur as B12 and folate deficiencies progress?

A

Pancytopenia (low platelets and neutrophils)

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12
Q

What is vit B12 deficiency also associated with?

A

Neurological disease - focal demyelination affecting spinal cord, peripheral nerves and optic nerve

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13
Q

Clinical presentation in sickle cell

A
  • Symptoms of anaemia usually mild as HbS readiy gives up oxygen in comparison to HbA
  • Crisis (vasoocclusive, aplastic, haemolytic)
  • Other organ damage
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14
Q

How does a cell become sickle shaped?

A

When the cell becomes deoxygenated the HbS polymerise, repeated cycles of deoxygenation cause the erythrocyte to become irreversibly sickled. Could lead to thrombosis

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15
Q

Things that may cause a sickle cell crisis

A

Cold, infection, stress

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16
Q

Sickle cell critical blood vessel locations

A
  • Stroke
  • Lung infarcts
  • Atrophic spleen due to multiple infarcts
  • Avascular necrosis and ulceration of skin at femoral head
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17
Q

Where is thalassaemia prevalent?

A

South Asia, Mediterranean and Far East

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18
Q

Extramedullary haematopoiesis

A

An attempt to compensate for lack of erythrocytes but results in splenomegaly, hepatomegaly and expansion of haemopoiesis into the bone cortex, this impairs growth and causes classical skeletal abnormalities

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19
Q

Premature death in thalassaemia due to:

A

Iron overload, excessive absorption or dietary iron due to ineffective haematopoiesis

20
Q

Treatment of thalassaemia

A
  • Transfusions
  • Iron chelation
  • Folic acid
  • Immunisation
  • Stem cell transplantation in some
21
Q

Beta thalassaemia major

A

Severe, transfusion dependent anaemia that first manifests 6-9 months after birth as synthesis switches from HbF to HbA. Either type beta o or beta (Bo/Bo or B/B)

22
Q

Beta thalassaemia trait

A

Usually asymptomatic with mild anaemia

23
Q

Beta thalassaemia intermedia

A

Mild variants of homozygous Bthalassaemia or severe variants of heterozygous thalassaemia

24
Q

Alpha thalassaemia silent carrier

A

Deletion of a single alpha globin gene, asymptomatic, without anamia

25
Q

Alpha thalassaemia trait

A

Deletion of two alpha globin genes. It may affect both genes of one chromosome or one gene of each chromosome. Minimal or no anaemia and no physical signs. Microcytosis and hypochromia visible

26
Q

Haemoglobin H disease

A

Deletion of three alpha globin genes. Tetramers of beta globin (HbH) are formed. Moderately severe anaemia. Microcytic, hypochromic anaemia with target cells and Heinz bodies in blood smear

27
Q

Hydrops fetalis

A

Deletion of all four alpha globin genes. In foetus, excess gamma globin chains form tetramers (Hb Bart) that are unable to deliver oxygen to the tissue, usually intrauterine death

28
Q

Aplastic anaemia

A

Refers to the inability of haematopoietic stem cells to generate mature blood cells

29
Q

Iron deficiency anaemia causes

A
  • Increased blood loss
  • Increased requirement (growth spurt in infancy, pregnancy, lactation)
  • Inadequate dietary supply
  • Decreased absorption (gastrectomy, coeliac disease)
  • Anaemia of chronic disease
30
Q

Reasons for anaemia in anaemia of chronic disease

A

Increased activity of macrophages reduces lifespan of red blood cells and signalling through the erythropoietin receptor is blunted. Cytokines such as IL-6 increase the production of hepcidin by the liver, resulting in less iron absorption

31
Q

Deficiency of B12 and folate leads to which type of anaemia?

A

Megaloblastic anaemia

32
Q

Role of tetrahydrofolate in metabolism

A
  • One carbon carrier
  • Accepts carbon units from serine, glycine, histidine and formate
  • Used to provide carbons for other metabolic reactions
  • Including synthesis of the base thymidine required for DNA synthesis, synthesis of purine bases adenine and guanine, and transfer of methyl groups to vitamin B12
  • In pregnancy can result in neural tube defects
33
Q

Metabolic reactions that B12 is required for

A
  • Transfers methyl group from L-methylmalonyl-CoA to form Succinyl-CoA
  • Transfer of methyl group from FH4 to homocysteine to form methionine (leads to functional folate deficiency)
34
Q

Hereditary spherocytosis: defect, features, treatment

A
  • Autosomal dominant
  • Defects in red blood cell membrane proteins
  • Mild to moderate anaemia
  • High levels of bilirubin in the blood
  • Splenomegaly
  • Reticulocytes in blood smear
  • Increased mean corpuscular hemoglobin concentration (MCHC)
  • Treatment is splenectomy
35
Q

Hereditary elliptocytosis

A
  • Defect in either structure or quantity of cytoskeletal proteins
  • 90% of cases asymptomatic
  • Disorder predisposes to haemolytic anaemia
  • Common for up to 15% of erythrocytes to be elliptical in the general population
  • Splenectomy can be performed in cases with splenomegaly
36
Q

Hereditary pyropoikilocytosis

A
  • Autosomal recessive
  • Clinically related to and considered to be the subtype to elliptocytosis
  • Defect in spectrin
  • Manifests as a severe haemolytic anemia with thermal instability of the red blood cells
  • Splenomegaly
  • Folate supplementation
37
Q

Hereditary stomatocytosis

A
  • Abnormal permeability of erythrocyte cell membranes to sodium and potassium
  • Mild to moderate anaemia
  • Splenomegaly and cholelithiasis
  • Elevated bilirubin
  • Treatment is folate supplements, chelation therapy may be required
38
Q

Acquired mechanical damage to red cell membrane results from:

A
  • Heart valves
  • Vasculitis
  • Microangiopathic haemolytic anaemia
  • Disseminated intravascular coagulopathy
39
Q

Red cell enzyme defects

A
  • Glucose 6 phosphate dehydrogenase deficiency

- Pyruvate kinase deficiency

40
Q

Autoimmune haemolytic anaemia classification

A
  • Warm (IgG, maximally active at 37degrees)

- Cold (IgM, maximally active at 4degrees)

41
Q

Key laboratory features of haemolytic anaemia

A
  • Increased reticulocytes
  • Raised bilirubin
  • Raised lactate dehydrogenase
42
Q

Myeloproliferative disorders

A
  • Essential thrombocythaemia
  • Polycythaemia Vera
  • Myelofibrosis
43
Q

Clinical features of myeloproliferative disorders

A
  • Overproduction of one or several blood elements
  • Hypercellular marrow/marrow fibrosis
  • Cytogenetic abnormalities
  • Thrombotic or haemorrhagic diatheses
  • Extramedullary haematopoiesis
  • Transformation to acute leukaemia
44
Q

Aetiology of myeloproliferative disorders

A

Point mutation in Janus kinase 2 gene (JAK2), a cytoplasmic tyrosine kinase on chromosome 9, which causes increased proliferation and survival of haematopoietic precursors.

45
Q

Polycythaemia Vera clinical features

A
  • Too many red blood cells produced
  • High haematocrit or red cell mass
  • Significant cause of arterial thrombosis
  • Venous thrombosi
  • Haemorrhage into skin or GI tract
  • Pruritis
  • Splenomegaly
  • Gout
  • In some transformation to myelofibrosis or acute leukaemia
46
Q

Erythrocytosis types

A

Increase concentration of RBC. Relative (normal cell mass, decreased plasma volume).
Absolute (increased red cell mass)
- Primary (polycythaemia vera)
- Secondary (driven by erythropoietin production, can be physiologically appropriate or inappropriate)

47
Q

Polycythaemia vera management

A
  • Venesection to maintain Hct to <0.45
  • Aspirin 75mg
  • Manage CVS factors
  • Drugs in some cases

MEH (12 decks)

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