Lecture 14: Blood Cell Abnormalities Flashcards
What is anaemia?
Reduction in amount of haemoglobin in given volume of blood below expected comparison w/healthy subject of same age and gender.
What are some mechanisms of anaemia?
- reduced production of red cells/haemoglobin in bone marrow
- loss of blood from body
- reduced survival of RBCs in circulation
- pooling of red cells in very large spleen
What is a microcytic red cell?
A red cell that is smaller than normal
What is a macrocytic red cell?
A red cell that is larger than normal
What are some common causes of microcytic anaemia?
- defect in haem synthesis –> iron deficiency, anaemia of chronic disease
- defect in globin synthesis (thalassaemia)–> defect in a-chain or B-chain synthesis
What are some causes of iron deficiency?
- Increased blood loss (menstrual, hookworm etc.)
- Insufficient intake (dietary, malabsorption - coeliac disease)
- Increased requirements (pregnancy, infancy, physiological)
What is often another characteristic of microcytic red cells?
They are usually also hypochromic (paler)
What can cause macrocytic anaemias?
Abnormal haemopoiesus so red cell precursors continue to synthesise haemoglobin and other cellular proteins but fail to divide normally
Red cells end up larger than normal
What is a megaloblast?
An abnormal bone marrow erythroblast - larger than normal and shows nucleocytoplasmic dissociation
What is megaloblastic anaemia caused by?
Deficiency of vitamin B12 or folate
What are some causes of normocytic anaemia?
- gastrointestinal haemorrhage
- trauma
- early stages of iron deficiency
- bone marrow failure or suppression
- bone marrow infiltration
- hypersplenism
- splenic sequestration
What is polycythaemia?
Too many red cells in circulation, increase in total volume
What can cause polycythaemia?
- blood doping or overtransfusion
- appropriately increased erythropoietin e.g. as result of hypoxia
- inappropriate erythropoietin synthesis or use e.g. from renal tumour secretions
- independent of erythropoietin: polycythaemia Vera, intrinsic bone marrow disorder that leads to thick blood
How should a blood count always be interpreted?
In context of clinical history and physical findings
What is leukaemia?
Bone marrow disease
What does leukaemia result from?
Series of mutations in single lymphoid or myeloid stem cell —> lead progeny of cell to show abnormalities in proliferation, differentiation or cell survival leading to study expansion of leukaemic clone.
What is chronic leukaemia?
Leukaemia that behaves in a ‘benign’ manner
What is acute leukaemia?
Leukaemia that behaves in a ‘malignant’ way, aggressive, patient dies quite rapidly
What cells does lymphoid leukaemia affect?
B, T or NK cells/lineage
What cells does myeloid leukaemia affect?
Any combination of granulocytic, moncytic, erythroid, megakaryocytic
What are the 4 types of leukaemia?
- acute lymphoblastic leukaemia (ALL)
- acute myeloid leukaemia (AML)
- chronic lymphocytic leukaemia (CLL)
- chronic myeloid leukaemia (CML)
What are some recognised leukaemogenic mutations?
- mutation in known proto-oncogene
- creation of novel gene e.g. chimaeric or fusion genes
- dysregulation of gene when translocation brings it under influence of promoter or enhancer of another gene
Name some identifiable causes of leukaemogenic mutations.
- irradiation
- anti-cancer drugs
- cigarette smoking
- chemicals, benzene
In AML, what happens as the cells continue to proliferate but no longer mature?
There is:
- a build up of most immature cells(myeloblasts or ‘blast cells’) in bone marrow which spreads into blood
- failure of production of normal functioning end cells such as neutrophils, monocytes, erythrocytes and platelets
