Intro to anaemia
Anaemia is characterised by reduced haemoglobin in the blood. This can be caused by many things and can take many forms as well.The three main classes are: microcytic anaemia, normocytic anaemia, and macrocytic anaemia. You can also have hypochromic, normochromic anaemia which roughly describe the concentration. of haemoglobin in each RBC.
General signs and symptoms:
Symptoms:
Symptoms can be mild and often can be none
- weakness and fatigue,
- short of breath
- heart racing and palpiationis
- feel cold With vascular disease
- angina
- claudication
Signs:
- pallor of mucous membranes
- increased pulse rate Severe anaemia
- heart failure and increased pulse rate Severe anaemia with vascular disease
- Confusion
- Myocardial ischaemia in ECG/exercise test
General aetiology of anaemia
Anaemias can either be due to reduced production of RBC/Haemoglobin or increased destruction of RBCs.
additionally often the anaemia is named after the cause (Anaemia of inflammation)
General tests for anaemias
- Blood count & Blood film examination Especially useful for determining
- Reticulocyte count
- BIlirubin test
- breakdown product for
- Haptoglobin test
- Protein that mops up haemoglobin. In haemolysis it is used up and will be low in the blood.
Microcytic anaemias
Microcytic anaemia is anaemia where the RBCs are smaller. They are smaller because they contain less haemoglobin, and often can be described as hypochromic, but not always,
This is stated to be because of 3 (main) things which are:
Causes of microcytic anaemia
Iron deficiency
Iron deficiency mean less haemoglobin made and therefore smaller amounts of haemoglobin made for each new cell.
Thalassaemias
Thalassaemia is better explained in the Thalassaemia reference page. Thalassaemia is a gneetic condition where your body cannot properly produce one of the subunits for haemoglobin correctly and therefore cannot produce haemoglobin. This leads to microcytic, hypochromic anaemia but occurs on a spectrum.
Inflammation
This occurs when the body is under systemic inflammation. The macrophages (which are the arbiters of iron in the body) hold onto iron and the bacteria cannot get onto it. Incidentally your marrow cells also cannot get onto it to make haemoglobin.
Generally these causes are strung together by things that cause reduced production of haemoglobin. Less produced haemoglobin leads to less haemoglobin in each cell, leading to smaller, hypochromic cells,
Normocytic anaemias
Normocytic anaemia occurs when each cell is the correct size, but either are in small number (decreased production or increased destruction) or are hypo-chromic.
Causes:
Decreased production
Renal disease
When the kidneys is in acute disease they produce less erythropoietin, the hormone needed for RBC production
Malignancy
Cancer can push out normal bone marrow cells which lead to reduced production of RBC and therefore anaemia
Bone marrow disease
If there is disease that damages the bone marrow, like a viral infection for example
Inflammation
Inflammatory anaemia is tends towards being microcytic but can present as normocytic
Increased destruction Both of these can tend towards macrocytic anaemia upon replenishment.
Haemolytic causes
Increased breakdown of cells can cause less total circulating RBCs, resulting in anaemia, some examples are: autoimmune disease, malaria, hereditary spherocytosis, etc.
Acute bleeding and following haemodilution
If there is a lot of blood loss that is stopped there will be less liquid and therefore hydrostatic pressure in capillaries. Interstitial fluid will seep into the capillaries diluting the blood and leading to Haemodilution, leading to less total RBCs per unit plasma and anaemia
Macrocytic anaemias
Macrocytic anaemias are funny, they are anaemia where the RBC are very big, and yet the total Hb in blood is decreased. often this is due to one of the following factors:
Causes:
Liver disease
delayed erythropoiesis
Increased RBC production
Paradoxically you can see anaemia with large RBCs when there is high rates of RBC replenishment. This is because the RBCs leave the marrow as reticulocytes when rushed, which still have a nucleus, meaning they are bigger then the RBCs.
Summary graph
Source content
Overview of anaemias, Ian Morison, blood lecture 2