Week 1: Outline the mechanisms of Anaemia Flashcards
What is anaemia?
Anaemia is caused by a reduced number of red blood cells in circulation, or a decreased amount of haemoglobin in the red blood cells
This results in reduced levels of oxygen delivery to tissues
Anaemia may be significant before a patient appears pale
What are signs of anaemia?
Pallor (especially of the conjunctiva)
Tachycardia (Pulse rate over 100 beats per minute)
Glossitis (swollen and painful tongue - reasonably specific for vitamin B12 deficiency)
Koilonychia (spoon nails - reasonably specific for iron deficiency)
Dark Urine ( in haemolytic anaemia)
What is the aetioological classification of anaemia?
Write down the process of erythropoesis
What takes place in the blood and the bone marrow in Erythropoiesis?
The final conversion from reticulocytes to erythrocytes
What is a sign of anaemia in regards to number of reticulocytes?
Higher number of reticulocytes means earlier release of immature RBCs to compensate for breakdown of red blood cells elsewhere
What is the precursor for all Blood cells?
Multipotential hematopoietic stem cell
What is the relationship between erythropoietin and tissue oxygenation?
They are inversely related
Erythropoietin can increase up to 1000X in response to anaemia
What controls the production of erythropoietin?
The juxtatubular interstitial cells of the renal cortex produce approximately 90 percent of the EPO in blood. They sense oxygen levels through oxygen-dependent prolyl hydroxylase that regulates the stability of the primary transcription factor for EPO, hypoxia-inducible factor 1(alpha) (HIF-1(alpha)).
How is erythropoiesis regulated?
1) The juxtatubular interstitial cells of the renal cortex detect hypoxia and increase levels of HIF1 alpha
As the HIF1 alpa levels increase, this increases EPO production.
2) As EPO increases, this increases production of erthryocytes.
3) As there are more erythrocytes, this decreases levels of hypoxia detected by kidney
4) The lower levels of hypoxia means less HIF1 alpha is produced and therefore less EPO is produced.
What anaemia can occur from changes in the bone marrow?
Conditions affecting specifically erythropoiesis in the bone marrow are described as pure red cell aplasia (PRCA)
Conditions affecting production of other cell types in addition to RBCs (white cells and platelets) is termed pancytopenia
The most common congenital PRCA is Diamond-Blackfan anaemia, which occurs due to reduced proliferation of erythroblasts. This is a rare condition, occurring in ~5 lives births/million.
Acquired PRCA can be classified as either primary (idiopathic – where no clear cause can be identified) or secondary (acquired as a result to exposure to a pathogenic agents such as a drug or infection)
What leads to HSC exhaustion?
When HSC DNA changes due to a chemical or genetic insult, the self-renewal process won’t happen and this means the pool of HSCs are not maintained. This can lead to pancytopenia.
Define Pancytopenia
A condition in which there is a lower-than-normal number of red and white blood cells and platelets in the blood. Pancytopenia occurs when there is a problem with the blood-forming stem cells in the bone marrow.
Define Aplastic Anemia
Aplastic anaemia is a serious condition affecting the blood, where the bone marrow and stem cells do not produce enough blood cells
Define Pure Red Cell Aplasia
Pure red cell aplasia (PRCA) is a rare disorder of blood production in which the bone marrow, the spongy tissue in the center of the bones, fails to function in an adequate manner resulting in anemia.