anaemia Flashcards
what is anaemia?
- reduction in amount of Hb in a given volume of blood
- Hb reduced
- often RBC and PCV/Hct reduced
what are the 4 mechanisms of anaemia?
- reduced proportion of RBCs/Hb in bone marrow
- loss of blood from body
- reduced survival of RBCs in body
- pooling of RBCs in spleen
what is it called when there is a reduced synthesis of haem?
iron def
what is it called when there is a reduced synthesis of globin?
beta-thalassaemia
what is microcytic anaemia usually?
hypochromic
what are the common causes of microcytic anaemia?
- defect in haem synthesis (iron def, anaemia of CD)
- defect in globin synthesis (thalassaemia)
what is normocytic anaemia normally?
usually often normochromic
what is macrocytic anaemia usually?
normochromic
what is macrocytic anaemia usually a result of?
abnormal haemopoiesis –> RBC precursors continue to synthesise Hb and other cellular proteins but don’t divide properly –> end up larger than normal
what are the causes of macrocytic anaemia?
- megablastic erythopoiesis (delay in maturation of nucleus while cytoplasm continues to mature and cell continues to grow)
- premature release of cells from bone marrow (young red cells are 20% larger)
define megaloblast
abnormal bone marrow erythroblast –> larger than normal, shows nucleocytoplasmic dissociation
what are the common causes of macrocytic anaemia?
- megaloblastic anaemia (lack of Vit B12, folic acid)
- DNA synthesis interfering drugs
- liver disease, ethanol toxicity
- recent major blood loss (body pumps out more reticulocytes)
- HA (RBCs lyse in blood stream, reticulocyte numbers inc)
what are the mechanisms of normocytic normochromic anaemia?
- recent blood loss (peptic ulcer, trauma)
- failure of production of red of red cells (beginning of iron def, renal failure, bone marrow failure)
- pooling of RBC in spleen
what is haemolytic anaemia?
shortened survival of RBCs in circulation
what can haemolysis occur from?
- intrinsic abnormality of red cells
- extrinsic factors acting on normal red cells
what 2 things can haemolytic anaemia be classed as?
- inherited: abnormalities in cell membrane, Hb, enzymes of RBC
- acquired: extrinsic factors e.g. microorganisms, drugs, chemicals
in what other way can HA be classed?
- intravascular: due to acute damage to RBC
- extravascular: defective RBCs removed by spleen
when do you suspect HA?
- otherwise unexplainable anaemia which is normochromic
- morphologically abnormal cells
- inc. RBC breakdown
- inc. bone marrow activity
- irregularly contracted cells, SC disease
what do people with HA potentially have?
- gall stones: high excretion of bilirubin
- jaundice: sickle cell, RBCs breaking down quickly
- polychromic anaemia (antibodies remove membrane of spherocytes, lyse cells)
name a disease where the defect lies in the RBC membrane
hereditary spherocytosis
name a disease where the defect lies in the Hb
sickle cell anaemia
name a disease where the defect lies in glycolytic pathway
pyruvate kinase def
name a disease where the defect lies in the pentose shunt
glucose-6-phosphate dehydrogenase def
name a disease that is caused by immune damage to the RBC membrane
AI Heamolytic anaemia
name a disease that is caused by mechanical damage to the whole red cell
microangiopathic haemolytic anaemia
name a disease that is caused by oxidant damage to the whole red cell
drugs and chemicals
name a disease that is caused by microbiological damage to the whole red cell
malaria
how does hereditary sphericytosis cause HA?
- intrinsic defect in RBC membrane
- red cells become less flexible
- removed by spleen prematurely
- causes extravascular (in spleen) haemolysis
- bone marrow responds –> inc. output of reticulocytes
- get polychromasia
what is the treatment of hereditary spherocytosis?
- splenectomy
- good diet/folic acid tablets (so don’t get folic acid def)
how does G6P dehydrogenase def cause HA?
- G6PD is important enzyme in pentos-phosphate shunt
- essential for protection of RBCs from oxidant damage
- oxidants may be generated in blood stream
G6PDD intrinsically affects RBCs –> HA - extrinsic oxidants = food, chemicals, drugs
what does G6PDD cause?
intermittent severe intravascular haemolysis
what are Heinz bodies?
- G6PDD intravascular haemolysis –> lots of irregularly contracted cells
- Hb becomes denatured –> forms round balls = heinz bodies
what causes autoimmune HA?
- production of autoantibodies directed at directed at RBC anitgens
- splenic macrophage recognised antibody and removes parts of RBC membrane –> spherocytosis
- spherocytes are less flexibke
- dec. flexibility and antigen recognition –> removal of RBCs from circulation
how do you diagnose autoimmune HA?
- spherocytes and inc. reticulocyte count on film
- detecting immunoglobulin of red cell surface
- detecting antibodies to RBC antigens
how do you treat autoimmune HA?
- corticosteroids
- splenectomy for severe cases
