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Anaemia 2 (Pernicious Anaemia (Pathophysiology (Intrinsic factor is…
Anaemia 2
Pernicious Anaemia
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Pathophysiology
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B12 and folate are required to convert deoxyuridine monophosphate to deoxythmidine monophosphate - this is needed for DNA synthesis
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Investigations
Blood film: anisocytosis and poikilocytosis, large macrocytes
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FBC: Hb is very low, MCV is very high, WCC and platelets are low
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β-Thalassaemia
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Pathophysiology
Excess α chains combine with whatever β , δ, γ chains are produced
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Excess of α chains. These precipitate in erythroblasts and red cells, causing ineffective erythropoiesis and haemolysis
Overall, a combination of ineffective erythropoiesis and haemolysis by the spleen
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Signs
β Thalassaemia Minor
Anaemia is mild, well tolerated or absent
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β Thalassaemia Major
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Extramedullary haemopoiesis occurs - RBCs are made outside the marrow. Causes characteristic head shape and hepatosplenomegaly
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Sickle Cell Anaemia
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Pathophysiology
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Flexibility of cells is decreased, they become rigid
Homozygote = sickle cell anaemia, heterozygotes = sickle cell trait, which protects against falciparum malaria
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Sickling leads to abnormal RBC lifespan and impaired passage of cells through microvasculature leading to obstruction and infarction of tissue
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Precipitated by infection, dehydration, cold, acidosis or hypoxia
Amino acid substitution in genes coding for beta chains - glutamine is swapped for valine at position 6
Signs
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Acutely painful hands and feet, triggered by cold, dehydration, infection, hypoxia
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Folate Deficiency
Folate Physiology
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Maternal folate deficiency causes foetal neural tube defects so mother must take folic acid supplements in first trimester
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Folate is found in green veg, nuts, yeast and liver
Causes of Deficiency
Increased cell turnover e.g. haemolysis, malignancy, inflammatory disease
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Pathophysiology
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B12 and folate are required for conversion of deoxyuridine monophosphate into deoxythymidine monophosphate - this is required for DNA synthesis
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Haemolytic Anaemia
Definition
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Extravascular = Occurs in reticuloendothelial system e.g. spleen, liver, bone marrow
Acquired Causes
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Immune Mediated
Autoimmune haemolytic anaemia - mediated by autoantibodies causing extravascular haemolysis. Classify according to optimal binding temp to RBCs. Warm is IgG mediated, binds at body temp. Cold is IgM mediated and binds at temp <4 degrees
Paroxysmal cold haemoglobinuria - seen with viruses, syphilis. Caused by antibodies sticking to RBCs in the cold and haemolysis when rewarmed
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Genetic Causes
Membrane defects
Hereditary spherocytosis - autosomal dominant. Less deformable spherical RBCs which get trapped in microvasculature of spleen
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Enzyme defects
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Pyruvate kinase deficiency - autosomal recessive. Decreased ATP production causes decreased RBC survival. Most are asymptomatic. Oxidative crisis due to decreased glutathione production, precipitated by drugs
Investigations
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Indirect Coombs test detects antibodies against RBCs that are free in serum. Serum is incubated with RBCs of known antigenicity
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