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Mechanisms of Anaemia:
What is Anaemia and the Red Blood Cell Role?
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Anaemia is a reduction in the number of red blood cells OR a reduction in the
quantity of haemoglobin
...
They have
thin cell membranes which allow oxygen and carbon dioxide to diffuse rapidly
and bind to the haemoglobin
...
They develop in the
bone marrow and LACK a nucleus
...

2) Free haemoglobin would also block + damage the kidneys
...
4 million red blood cells are made every second
...


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Each normal red blood cell:
1) LASTS FOR 120 DAYS
...

3) Travels 200km
...

➢ To synthesise protein after 24 hours  can only synthesise protein in
these first 24 hours due to residual RNA – these early red blood cells
are called reticulocytes
...

➢ Use oxygen (although they transport it)
...


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A red blood cell is ABLE:
➢ To metabolise glucose to ATP for energy
...

➢ Catabolise RNA
...

➢ Enzymes 
1) For glucose metabolism
...

3) Others
...
This enables it to squeeze through capillaries
...

➢ Responsive to fluid stresses so will deform in response to fluid pressure
...

➢ Has linear deformation up to 250%
...


-

The red blood cell membrane contains lots of membrane proteins which are
important for transporting molecules across the membrane and its stability
...

These proteins in the membrane include:
1) ANKYRIN  this links the bilayer to the membrane skeleton
...
IR COMPLEX  these are proteins which interact with the
protein 4
...


Anaemia:
-

Anaemia refers to a reduction in haemoglobin below the normal range
...


-

ANEAMIA IS:
➢ ADULT MALE  less than 130g/l
...


➢ ONE DAY OLD BABY  less than 160g/l
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➢ This would show up as a low reticulocyte count
...

➢ They would be pale – appear hypochromic
...

➢ This would mean the reticulocyte count is higher or the same as
normal
...


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The red blood cells are produced in the red bone marrow which is stimulated by
the hormone erythropoietin from the kidney
...


Mechanisms of Anaemia:
-

REDUCED BONE MARROW PRODUCTION:

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Haematinic Deficiency:
➢ Deficiencies of vitamin B12, folic acid and iron (which also causes
low iron) can cause reduced RBC production
...


-

Ineffective erythropoiesis
...


-

Infiltration of bone marrow
...


Iron Deficiency:
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Iron is needed for the synthesis of HAEM
...


-

Adults need 1mg of iron per day
...


-

Iron is absorbed in the DUODENUM
...


-

CAUSES of iron deficiency include:
1) Children:
➢ Dietary deficiency
...

➢ Bleeding due to HOOKWORM – this is the most important worldwide
cause of iron deficiency
...
Intestinal
malignancies can cause anaemia
...

➢ Coeliac Disease
...
This causes the ferritin levels in
the blood
...
This can be measured by a blood test
...
This anaemia is MICROCYTIC (small size of RBC)
and HYPOCHROMIC (pale)
...

4) Epithelial changes such as stomatitis (around the mouth) and koilonychias
(concave nails)
...


-

Both of these vitamins are needed for DNA synthesis and cell division
...

2) Asynchrony between the development of the nucleus and RBC – the nucleus
persists and remains larfe
...

4) B12 deficiency

is

also associated with

neuropathy

with sub-acute

degeneration of the spinal cord
...
These food products are digested to
release the B12 from enzymes
...


-

The B12-Intrinsic Factor complex can then be absorbed in the terminal ileum
...


-

CAUSES of B12 deficiency include:
1) Malabsorption:
➢ Pernicious Anaemia – this is an autoimmune disease where antibodies
are produced which destroy the parietal cells of the stomach
...
Can be treated
with B12 injections
...
This may result from
inflammatory bowel conditions like Crohn’s Disease or due to gastric
banding
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2) Dietary deficiency – vegans
...


Folate Deficiency:
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Folate deficiencies can be caused by:
1) Malabsorption:
➢ Tropical Sprue
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2) Dietary deficiencies
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4) Some drugs:
➢ Certain drugs alter or interfere with the metabolism of folate
...


Anaemia of Chronic Disease:
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Chronic inflammation CAN cause anaemia
...


-

This is linked to conditions such as:
1) Inflammatory bowel disease
...

3) Rheumatoid arthritis
...

➢ There are HIGH HEPCIDIN LEVELS
...
High hepcidin levels cause LESS iron absorption
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➢ There may be NO erythropoietin produced if impaired kidneys – need
injections
...


Aplastic Anaemia:
-

Aplastic anaemia is a disease where the bone marrow is damaged
...
This is pancytopenia
...


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CAUSES of APLASTIC anaemia include:
1) Idiopathic causes
...

➢ May be unpredicatable such as Chloramphenicol or Gold
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4) Infections like viral hepatitis
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Ineffective Erythropoiesis:
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When there is ineffective erythropoiesis, the bone marrow is ACTIVE but the
red blood cells produced develop abnormally
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-

Inherited forms of this include THALASSAEMIA
...

➢ The marrow in this is cellular + expanded causing expanded and damaged
bones
...

➢ This anaemia causes death if there is no transfusion
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➢ Thalassaemia affecting the beta-chain affects children once they are
born since the beta chain is only in HbA
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➢ Treatment is via blood transfusions + chelation therapy to prevent iron
overload
...

➢ There is a clonal population of abnormal marrow cells which have abnormal
chromosomes
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➢ It can produce isolate anaemia – refractor anaemia and refractor
anaemia with ring sideroblasts
...


-

There are primary bone marrow diseases including:
1) Leukaemias (acute, chronic, myeloid + lymphoid)
...

3) Myelomas – affecting the B-Cells
...


-

Other malignancies such as breast, lung, prostate, bowel, kidney and thyroid may
also cause anaemia
...


-

A chronic loss of blood is likely to present as iron deficiency
...

❖ Occurs due to leaking prosthetic metal heart valves which
damage RBC as they pass through
...
Coli infection
which causes kidney failure and haemolysis
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❖ March Haemoglobinuria – this occurs due to footstrike in
marathon running
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2) ABNORMAL RED BLOOD CELLS:
➢ Acquired abnormalities  immune haemolysis
...

❖ Can also be autoimmune
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❖ Red Cell Enzyme Defects such as G6PD deficiency and
Pyruvate Kinase deficiency
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