Blood Cell Abnormalities Flashcards
(31 cards)
What is anaemia?
•Reduction in the amount of haemoglobin in a given volume of blood below what would be expected in comparison with a healthy subject of the same age and gender
- By definition, the haemoglobin concentration (Hb) is reduced
- The RBC and the Hct/PCV are usually also reduced
What is the mechanism of anaemia?
- Reduced production of red cells/haemoglobin in the bone marrow
- Loss of blood from the body
- Reduced survival of red cells in the circulation
- Pooling of red cells in a very large spleen
What is an example of a cause and a mechanism?
Mechanism: might be reduced synthesis of haemoglobin in bone marrow
Cause: either a condition caused reduced synthesis of haem or one causing reducing synthesis of globin
Why use cell size?
-Sometimes neither mech or cause obvious so classification is on basis of cells size can help to suggest specific cause
•Microcytic – usually also hypochromic
•Normocytic – usually also normochromic
•Macrocytic – usually also normochromic
Describe microcytic anaemia
•A microcytic anaemia is one in which average cell size is decreased
What are the causes of iron deficiency with increased loss?
- Commonest cause in adults
- Hookworm commonest cause worldwide
- Menstrual (menorrhagia)
What are the causes of iron deficiency with insufficient intake?
- Dietary
- Vegetarians
- Malabsorption
- Coeliac disease (gluten-induced enteropathy)
- H. pylori gastritis
What are the causes of iron deficiency with increased requirements?
- Physiological
- Pregnancy
- Infancy
What are the three types of anemia?
- Microcytic
- Normocytic
- Macrocytic
What are the four mechanisms for anemia?
- Reduced production by the bone marrow
- Loss of blood from body
- Reduced survival of red cells in circulation
- Pooling of red cells in a very large spleen
- Cells may be normal, large or small
What are the different types of polycythaemia?
- Pseudo (reduced plasma volume can be acute e.g. suddenly water loss or dehydration or chronic e.g. prescribed drug to pass lots of urine or other chronic condition unexplained)
- True with an increase in total volume of red cells in circulation
What are some of the true reasons you might have polychthaemia?
- Blood doping or over transfusion e.g. blood doping
- Appropriately increased erythropoietin e.g. hypoxia
- Inappropriate erythropoietin synthesis or use e.g. blood doping or cancer which leads to synthesis of erythropoietin e.g. rumour of kidney which inappropriately secretes erythropoietin
- Independent of erythropoietin e.g. intrinsic bone marrow disorder called polychythaemia vera
Why do people get anemia?
- Anaemia is usually due to a reduction of the absolute amount of haemoglobin in the blood stream
- Occasionally a low Hb results from an increase in plasma volume
- In a healthy person, anaemia resulting from an increase in plasma volume cannot persist because the excess fluid in the circulation is excreted
- For practical purposes, anaemia can therefore be regarded as a resulting from a decrease in the absolute amount of haemoglobin in the circulation
What are the common causes of microcytic anaemia?
- Defect in haem synthesis
•Iron deficiency
•Anaemia of chronic disease* - Defect in globin synthesis (thalassaemia)
•Defect in α chain synthesis (α thalassaemia)
•Defect in β chain synthesis (β thalassaemia)
What are different types of cells?
Small cells: microcytosis (low MCV)
Pale cells: Hypochromia (low MCHC)
Occasional target cells
‘Pencil cells’ (elliptocytes)
What is macrocytic anaemia?
•A macrocytic anaemia is one in which average cell size is increased
Where do microcytic anaemias result from?
- Macrocytic anaemias usually result from abnormal haemopoiesis so that the red cell precursors continue to synthesize haemoglobin and other cellular proteins but fail to divide normally
- As a result, the red cells end up larger than normal - Megaloblastic erthpoeisos
What is Megaloblastic erthpoeisos?
- One cause of macrocytic anaemia is megaloblastic erythropoiesis
- This refers specifically to a delay in maturation of the nucleus while the cytoplasm continues to mature and the cell continues to grow
- Megaloblasts are generally seen in the bone marrow, not the blood film
What is a megaloblast?
- A megaloblast is an abnormal bone marrow erythroblast
* It is larger than normal and shows nucleocytoplasmic dissociation
What is megaloblastic anaemia caused by?
- Megaloblastic anaemia is caused by a deficiency of vitamin B12 or folate
- It is possible to suspect megaloblastic anaemia from the peripheral blood features but to be sure requires bone marrow examination
What are common causes of microcytic anemia?
- Lack of vitamin B12 or folic acid (megaloblastic anaemia)
- Use of drugs interfering with DNA synthesis
- Liver disease and ethanol toxicity
- Recent major blood loss with adequate iron stores (reticulocytes increased)
- Haemolytic anaemia* (reticulocytes increased)
What is important to remember about young red cells?
Young red cells are about 20% larger than mature red cells so if there is an increased proportion of young red cells (polychromasia/reticulocytes) in the circulation, the average cell size (MCV) will be increased
What is the mechanisms of normocytic anaemia?
-Recent blood loss: e.g. of causes gasointesitinal haemorrhage, trauma
-Failure of production of red cells e.g. of causes Early stages of iron deficiency
Bone marrow failure or suppression (e.g. chemotherapy)
Bone marrow infiltration (e.g. leukaemia)
-Pooling of red cell in the spleen e.g. of causes Hypersplenism, e.g. liver cirrhosis
Splenic sequestration in sickle cell anaemia
What is polycythsemia?
- Polycythaemia literally means ‘many cells’ but it refers specifically to too many red cells in the circulation
- The Hb, RBC and Hct are all increased compared with normal subjects of the same age and gender
