anaemia Flashcards
what is anaemia
reduction in amount of hb in a given vol of blood (below what is expected in comparison with healthy subject of same gender and age)
what are the mechanisms leading to anaemia
reduced production of red cells/hb in bone marrow
loss of blood from body
reduced survival of red cells in circulation
pooling of red cells in enlarged spleen
how can we determine cause of anaemia
classification on basis of cell size
helpful to look at mcv (average size of rbcs)
what does microcytic mean
describes red cells that are smaller than normal/ anaemia with small red cells
what does normocytic means
describes red cells with normal size/anaemia with large red cells
what does macrocytic mean
red cells that are larger than normal/ anaemia with large cells
how can we tell if red cells are normachromic
have about a third of diameter is pale - this is result of disc shape
what does hypochromia mean
cells have larger area of central pallor than normal more than 1/3 of diameter
- results from lower hb conc and flatter cells
why do hypochromia and microcytosis oftern go together
they both result from defect in hb synthesis
not enough hb = smaller cells and conc of hb reduced
what are some common causes of microcytic anaemia
defect in haem synthesis: iron def anaemia and anaemia of chronic disease
defect in globin synthesis:
alpha thalasaemia
beta thalasaemia
what are some causes of iron def anaemia
- increased blood loss: commonest cause in adults, hookwork, menorrhagia, bleeding due to colon cancer
- insufficient intake - dietary
- decreased absorption - coeliac disease, h- pylori gastritis
increased requirements - physiological, pregnancy and infancy
meds e.g aspirin/nsaids
what would you expect to see in bloods of individual with anaemia of chronic disease
low hb low/normal mcv high ferritin! low serum iron low/normal transferrin high esr
what would you expect to see in bloods of individual with iron def anaemia
low hb low mcv low ferritin low serum iron high transferrin may be high esr
what is macrocytic anaemia
average cell size is increased
usually result from abnormal haemopoiesis so red cell precursors continue to synthesise hb but fail to divide normally
what is a cause of macrocytic anaemia
megaloblastic erythropoiesis
- refers to delay in maturation of nucleus while cytoplasm continues to mature and cell continues to grow.
megaloblasts usually seen in bone marrow
what is megaloblastic anaemia
caused by deficiency of b12/folate
what would yo expect to see in megaloblastic blood film
anaemia
tear drop cells
hypersegmented neutrophils
oval macrocytes
what are some common causes of macrocytic anaemia
lack of b12/folic acid = megaloblastic anaemia
use of drugs interfering with dna synthesis
liver disease and ethanol toxicity
haemolytic anaemia
what are some mechanisms of normocytic anaemia
recent blood loss
failure of production of red cells
pooling of red cells in spleen
causes of reduced red cell production
iron def anaemia
anaemia of chronic disease
megaloblastic anaemia
what is haemolytic anaemia
form of anaemia due to hemolysis, abnormal breakdown of rbcs, either in blood vessels or elsewhere in body
what are some symptoms of haemolytic anaemia
fatigue and shortness of breath
- breakdown of red cellls also leads to jaundice and increases risk of particular long term complications e.g gallstones and pulmonary hypertension
what can hereditary haemolytic anaemia be due to
defects in rbc membrane - hereditary spherocytosis
defects in hb production- thalasaemia, sickle cell disease
defective red cell metabolism- g6pd def
what can acquired haemolytic anaemia be due to
caused by immune mediated causes, drugs, others e.g autoimmune haemolytic anaemia (more common in sle,ra…)
- any causes of hypersplenism
what does erythrocyte function depend on?
integrity of membrane
hb structure and function
cellular metabolism
differences between haemolysis and haemolytic anaemia
haemolysis = lowered rbc lifespan <120 days
haemolytic anaemia = cannot compensate for lowered rbc count
how do patients with chronic haemolysis get treated?
folic acid - due to increased dna synthesis
splenectomy (if severe) to increase red cell lifespan because spleen takes out rigid rbcs (spherocytes) out circulation
what should make you consider haemolysis
elevated reticulocytes/ldh/unconjugated bilirubin
what test can be used to confirm immune mechanism in haemolysis
DAT - Direct anti - globulin test
what does a high reticulocyte count mean
bone marrow responds to haemolytic anaemia by producing more rbcs
what are some oxidative stressors for g6pd deficiency
broad beans e.g fava beans quinine derived drugs certain antibiotics infections naphthalene
how to treat iron deficiency anaemia
oral iron supplements with orange juice
iv iron
what is anaemia of chronic disease put simply
body stores iron
what are some common causes of anaemia of chronic disease?
infections e.g tb/hiv
ra/ other autoimmune disorders
malignancy
