14 Blood cell abnormalities Flashcards
What is anaemia?
A reduction in the amount of haemoglobin in a given volume of blood (reduced Hb)
What (apart from Hb) is reduced in anaemia?
- RBC
- Hct (hematocrit - percentage volume of RBCs)
- PCV (packed cell volume)
What normally causes anaemia?
A reduction of the absolute amount of haemoglobin in the blood stream
Why can an increase in plasma volume not persist in healthy individuals?
The excess fluid is excreted (urine) and the plasma volumes are brought back to normal
What are the 4 mechanisms of anaemia?
- Reduced production of RBCs/haemoglobin in bone marrow
- Loss of blood from the body
- Reduced survival of RBCs in circulation
- Pooling of RBCs in a very large spleen
What are the probable causes of reduced synthesis of haemoglobin in the bone marrow?
Conditions causing
- Reduced synthesis of haem
- Reduced synthesis of globin
Namet wo causes of reduced synthesis of haem
- Iron deficiency
- Anaemia of chronic disease (chronic inflammation, Fe trapped in macrophages)
(lead?)
What is the name of a condition where there is an inherited defect leading to reduced globin production?
Thalassaemia
What is the main way of determining the cause of anaemia?
Classification on the basis of cell size
What is a microcyte?
A red cell smaller than normal
What is a normocyte?
A normal red cell (size + Hb)
What is a macrocyte?
A red cell larger than normal
What does hypochromic mean?
A red cell with less colour than normal (less Hb)
What does normochromic mean?
Concentration of Hb within cells is normal
Are microcytes typically hypochromic or normochromic?
Hypochromic
What two types of cells are normochromic?
- Normocytes
- Macrocytes
What are some common causes of microcytic anaemia?
- Defect in haem synthesis
- Defect in globin synthesis (thalassaemia)
What are the two types of thalassaemia?
α and β thalassaemia
- Defect in alpha chain synthesis
- Defect in beta chain synthesis
What are the causes of iron deficiency?
- Increased blood loss (commonest)
- Insufficient intake
- Increased requirement
What are some causes of increased blood loss?
- Hookworm
- Menstrual (menorrhagia)
What are some causes of insufficient intake?
- Dietary e.g. vegetarians
- Malabsorption (coeliac disease, H pylori gastritis)
What are the causes of increased requirements?
- Physiological e.g. during pregnancy, infancy
Why does macrocytic anaemia occur?
- Abnormal haemopoiesis –> red cell precursors continue to produce Hb and proteins but fail to divide normally
What are the common causes of macrocytic anaemia?
- Megaloblastic erythropoiesis
- Liver diseases/ethanol toxicity
- Major blood loss (increased reticulocytes)
- Haemolytic anaemia (increased reticulocytes)
What is megaloblastic erythropoiesis?
A delay in maturation of the nucleus while the cytoplasm continues to mature (cell grows)
Where are megaloblasts normally seen?
Bone marrow
not seen in the blood film
What causes megaloblastic anaemia?
- Deficiency of vitamin B12 or folate
- Use of drugs interfering with DNA synthesis (retarding nuclear development)
What is the difference between polychromasia and reticulocytosis?
Polychromasia
- RBCs with blue tinge, young cells, newly released
Reticulocytosis
- Increased number of young cells recognised by a specific stain
What are some causes of blood loss?
- Gastrointetinal haemorrhage
- Trauma
- Tissue damage
What are some causes of failed RBC production?
- Early stage Fe deficiency
- Bone marrow failure/suppression (chemotherapy)
- Bone marrow infiltration (leukemia)
What are some causes of pooling of RBCs in the spleen?
- Hyperslenism (liver cirrhosis)
- Splenic sequestration (SCA)
What is polycythaemia?
Too many red cells in circulation
What counts are increased in polycythaemia?
- Hb
- RBC
- Hct
What is pseudo polycythaemia?
Reduced plasma volume
What is true polycythaemia?
Increase in total volume of red cells in circulation
What are the 4 mechanisms of true polycythaemia?
- Blood doping/overtransfusion
- Increased erythropoietin
- Inappropriate erythropoietin synthesis or use
- Polycythaemia vera (intrinsic disorder of bone marrow)
What does polycythaemia vera cause?
Hyperviscosity (thick blood) leading to vascular obstruction
How is polycythaemia vera treated?
- Blood can be removed to reduce viscosity (venetriction)
- Drugs can be given to reduce bone marrow RBC production
What is a possible cause and mechanism of a raised Hb in a patient with an abdominal mass?
- Carcinoma of kidney
- Inappropriate erythropoietin synthesis
What is a possible cause and mechanism of a raised Hb in a breathless cyanosed patient?
- Hypoxia
- Appropriately increased erythropoietin
What is a possible cause and mechanism of a raised Hb in a patient with an enlarged spleen?
- Polycythaemia vera
- Abnormal bone marrow function
What is a possible cause and mechanism of a raised Hb in a young healthy athlete?
Blood doping or inappropriate erythropoietin use
Why might a person with blue lips develep polycythaemia?
Cyanosis –> Patient is hypoxic
What effects can polycythaemia due to hypoxia have?
- Can cause hyper-viscosity
- Predispose to thrombosis
What is leukaemia?
Cancer of the blood (5% of all cancers)
How does leukaemia occur?
Results from a series of mutations in a single lymphoid or myeloid stem cell
What do mutations in lymphoid/myeloid stem cells do?
Lead progeny of cell to show abnormalities in proliferation, differentiation or cell survival
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