Anaemia Flashcards
what is anaemia?
the oxygen carrying capacity of the blood drops below normal
what is anaemia in men?
<130g/L
what is anaemia in women?
<120g/L in non-pregnant women
what is anaemia in children?
<120g/L
symptoms of anaemia
easily fatigue low energy rapid heart beat SOB headaches difficulty concentrating dizziness pale skin leg cramps insomnia conjunctival pallor nail bed pallor
what causes anaemia?
decreased haemoglobin content within erythrocytes
decreased erythropoiesis
loss of erythrocytes - early destruction
what is haemoglobin?
respiratory pigment of many invertebrates and almost all vertebrates. It interacts with O2 and CO2
how much haemoglobin is there?
250 million haemoglobin molecules per erythrocyte
structure of haemoglobin
iron sitting below porphyrin ring in haem centre
bound to 1 axial histidine and 1 distal histidine residue of the globulin
4 of these structures - 2 alpha and 2 beta
red blood cells
biconcave discs
shape is vital to maintain adequate surface area so there is sufficient oxygen transfer
shape can change remarkable as they squeeze through capillaries
96-100% saturation in all cells
average number of RBCs in women
4.7million/mm3
average number of RBCs in men
5.2million/mm3
formation of an erythrocyte
proerythroblast
basophilic erythroblast
polychromatic erythroblast
normonblast/ orthrochromatic erythroblast
reticulocyte - released from bone marrow into blood and loses the remaining DNA
erythrocyte
what can haemoglobin carry?
CO2
NO
CO
O2
What happens in sickle cell anaemia?
haemoglobin forms chains in the cell and cause sickling of it.
They cannot move easily through capillaries and so form clots and are eliminated by macrophages in the spleen.
Causes splenomegaly
More RBCs need to be made to keep up with oxygen carrying requirements
Iron deficiency anaemia
leads to decreased amounts of haemoglobin
low levels of haemoglobin decreases the production of RBCs
what causes iron deficiency anaemia?
blood loss
diet low in iron
poor absorption of iron
pernicious anaemia and B vitamin deficiency
RBCs do not develop as they normally would because of a lack of B vitamins which leads to decreased production of RBCs
what are B vitamins?
B12 and folate
What are the causes of pernicious anaemia?
lack of intrinsic factor
diet low in B vitamins
decreased absorption of B vitamins
Aplastic anaemia
bone marrow is unable to produce enough blood cells
life threatening condition
what causes aplastic anaemia?
cancer therapy
exposure to toxic substances
autoimmune disorders
viral infections
Haemolytic anaemia
RBCs are destroyed faster than the bone marrow can replace them
what causes haemolytic anaemia?
inherited causes
sickle cell anaemia
thalassemia
anaemia of chronic disease
various illnesses over a long time can reduce the production of RBCs
what causes anaemia of chronic diseases?
rheumatoid arthritis kidney disease diabetes TB HIV
blood testing for anaemia
full blood count haemoglobin mean cell volume mean corpuscular Hb concentration haematocrit RBC count mean corpuscular Hb
what causes low haematocrit?
decrease in RBCs or increase in plasma volume, e.g. in pregnancy
what are the different classifications of anaemia?
MCV - microcytic/ normocytic/ macrocytic
MCHC - hypochromic/ normochromic
siberoblastic anaemia
group of blood disorders characterised by an impaired ability of bone marrow to produce normal RBCs
iron inside RBCs is inadequately used to make haemoglobin despite there being normal amounts of iron
therefore iron accumulates in the RBCs, giving a ringed appearance to the nucleus
anaemia of chronic disease presentation
RBCs are often normochromic normocytic but may show hypochromic microcytic indices similar to the effects of iron deficiency. Iron is stored away and not available for use. The difference is determined by measuring ferritin levels
Non-megaloblastic anaemia
no impairment of DNA synthesis occurs
includes disorders associated with increased membrane surface area, accelerated erythropoiesis and alcoholism
Hepatic disease
patients with hepatic disease have macrocytosis that is secondary to raised cholesterol and phospholipids deposited on membranes of circulating erythrocytes which increases the surface area of the erythrocyte
Affect of alcohol on anaemia
long-term alcohol excess suppresses bone marrow and has a direct toxic effect on developing erythroblasts. Often associated with folate deficiency
hypothyroidism
can cause anaemia that is usually normocytic or macrocytic because thyroid hormones stimulate the production of erythropoietin and affects haematopoiesis,, a reduction in thyroid hormones production may cause anaemia
iron deficiency
common cause of microcytic hypochromic anaemia
low iron = low Hb production
iron comes from dietary intake
what are the forms of iron?
- heme - from meat
2. non-heme - from leafy green veg
Importance of B12 and folate
both important for maturation process of reticulocytes so if there is a deficiency can cause pernicious anaemia. Immature RBCs can be released into the blood or reticulocytes may not mature fully
what happens to RBCs as they mature
get smaller in size
what causes macrocytic anaemia?
B12 and folate deficiency
B12 and folate deficiency
causes macrocytic/ megaloblastic anaemia as the RBCs are not extruded from the bone marrow at the correct time
what causes folate deficiency?
reduced intake
increased demand
malabsorption
drugs - anti-folates (methotrexate), folate not available for use
where does folate come from?
green veg
nuts
liver
there is a 4 month long store in the body
what causes B12 deficiency?
reduced intake - vegan diet
reduced intrinsic factor
reduced absorption
functional deficit
where does B12 come from?
stores last 4-7 years so it takes a long time for B12 deficiency/ anaemia to present itself
comes from meat, fish, dairy but not plants
what are B12 and folate needed for?
maturation of RBCs
what happens when there is B12 and folate deficiency?
immature RBCs are released into the blood prematurely
causes macrolytic anaemia because these cells have not undergone as many divisions
inhibits purine and thymidylate synthesis, impairs DNA synthesis and causes erythroblast apoptosis resulting in anaemia from ineffective erythropoiesis
absorption of vitamins
absorbed within small intestine by carrier mediated transport or passive diffusion
how is folate absorbed?
carrier-mediated transport
how is B12 absorbed?
too large to be absorbed by passive diffusion or carrier-mediated transport
B12 forms an acid-resistant complex with intrinsic factor in the stomach
the complex binds to specific receptors in mucosal cells in the terminal ileum
vitamin B12 is absorbed by endocytosis
vitamin B12 malabsorption
intrinsic factor secreted by gastric mucosa
atrophic gastric mucosa fails to secrete normal secretions
lack of intrinsic factor from cells of gastric glands
so there is no binding of vit. B12 to intrinsic factor
B12 is not protected from digestion by GI tract enzymes and so does not bind to receptor sites in cells of terminal ileum
failure to absorb vitamin B12 in GIT without intrinsic factor
causes pernicious anaemia
what occurs when there is a lack of absorption of B12 in lower ileum
no pernicious anaemia but type of B12 deficiency
posterior cord syndrome
B12 essential for maturation of other cells, e.g. neurons of dorsal column and mucosa in lining of mouth
deficiency causes instability and loss of ability to walk, large tongue, very large RBCs
MRI will show degeneration of dorsal columns
what is involved in iron studies?
ferritin - good marker of iron deficiency serum iron transferrin Fe saturation total iron binding capacity
how to treat iron deficiency anaemia?
blood transfusion
iron supplements
iron infusion
what happens if iron deficiency anaemia is left untreated?
heart attack
likely diagnosis if RBCs are microcytic?
iron deficiency anaemia
check ferritin/ iron studies
likely diagnosis if RBCs are macrocytic?
B12/ folate deficiency
check serum B12 and folate
How to treat anaemia?
treat according to underlying cause
