Red Cell Disorders Flashcards
Types of red cell disorders
Anaemia
Polycythaemia
Types of anaemia
Iron deficiency Megaloblastic Haemolytic Aplastic Sickle Thalassaemias
Clinical signs of anaemia
Reduced levels of Hb
Symptoms depend on severity - SoB, weakness/lethargy, tachycardia
Severe - potential for angina
Glossitis and angular cheilitis
DPG may be elevated in RBCs so O2 more readily given up in tissues
Characteristics of iron deficiency anaemia
microcytic, small, decreased MCV RBCs
Cause of iron deficiency anaemia
iron input reduced - poor diet, surgical removal of stomach
output increased - chronic/heavy menstruation, gastrointestinal bleeding (colon cancer?), ulcers (NSAIDs?)
demand increased - pregnancy
iron deficiency where bone marrow and macrophage Fe stores depleted, causing anaemia
Acute bleed
rapid blood loss as in haemorrhage
sever loss of blood
BP falls
over time there is haemodilution (more fluid in the blood)
Chronic bleed
long term bleeding
eg. gastric bleeding, excessive menstruation
How would Hb, haematocrit, MCV, retics, WBC, platelets, EPO and iron stores be affected 24 hours after an acute bleed?
Hb - decreased haematocrit - decreased MCV - normal retics - normal WBC - decreased platelets - decreased EPO - increasing iron stores - normal
How would Hb, haematocrit, MCV, retics, WBC, platelets, EPO and iron stores be affected after a chronic bleed?
Hb - decreased haematocrit - decreased MCV - decreased retics - increasing WBC - normal platelets - normal EPO - increased iron stores - zero
Treatment for iron deficiency anaemia
find and treat underlying cause
give oral iron (FeSO4)
prophylaxis in pregnancy - oral iron folic acid
severe - transfusion
What can renal anaemia lead to?
normocytic anaemia (normal size, not enough) complicates chronic renal failure
How to treat renal anaemia?
Fe and EPO
How does pregnancy affect RBCs?
dilution/iron effiency
therefore normocytic RBCs as pregnancy increases MCV but iron deficiency decreases MCV
What is megaloblastic anaemia?
abnormal RBC maturation due to defective DNA synthesis
out of step with cytoplasmic development, bone marrow contains megaloblasts
macrocytic
What is a megaloblast?
larger than normal RBC
cytoplasmic development quicker than DNA synthesis
What is the cause of megaloblast anaemia?
vitamin B12 or folate deficiency
Symptoms of megaloblast anaemia
jaundice - XS breakdown of Hb due to increased ineffective erythropoiesis
many symptomless and diagnosed with blood test
What is B12 essential for?
cofactor for purine and pyrimidine synthesis (therefore cell division), requires intrinsic factor for absorption
Use of folic acid (folate)
essential for thymidylate synthesis
rate limiting step in DNA snythesis as thymidine is a pyrimidine base
Action of folic acid and B12
methyl tetrahydrofolate and B12 as co-factor
THF -> THF polygultamate -> DHF reductase
causes deoxy-uracilmonophosphate (dUMP) to become deoxy thymine MP (dTMP)
DNA
Issues associated with B12 and folic acid
methotrexate
pernicious anaemia
Crohn’s disease
Methotrexate
problem
used in chemo, immunosupressant, rh. arthritis
inhibits dihydrofolate reductase
Pernicious anaemia
problem
lack of intrinsic factor for absorption of B12 due to automimmune disease
Crohn’s disease
malabsorption of B12, folate or iron
What happens in haemolytic anaemias?
increased rate of RBC destruction
eg. megloblastic
Types of haemolytic anaemias
spherocytosis
acquired
Spherocytosis anaemia
type of haemolytic anaemis
genetic
abnormal reduction in RBC membrane protein, fragile cells
Acquired anaemia
type of haemolytic anaemia
haemolytic transfusion reaction, malaria, drug-induced
Give consequences of haemolytic anaemias
jaundice and enlarged spleen
Cause of sickle cell anaemia
genetic - single nucleotide polymorphism
smino acid substitution, valine for glutamic acid
abnormal Hb - insoluble forms crystals at low O2, RBC form sickle shapes and may block microcirculation
What can sickle cell anaemia cause?
haemolytic anaemia
Cause of thalassaemias?
genetic
reduced rate of alpha/beta globin units production, variation
deletion of both alpha genes leads to death in uterus as Hb (gamma4) produced
one alpha gene deletion reduced RBC volume and haematocrit
What is aplastic anaemia?
insufficient production of RBCs, WBCs and platelets, although can be just RBCs
Consequences of aplastic anaemia
decreased resistance to infections, increased bleeding, increased tiredness
Cause of aplastic anaemia
viral, radiation, drugs cytotoxic agents chloramphenicol sulphonamides insecticides bone marrow failure
How to treat aplastic anaemia
bone marrow transplant with tissue match
immunosuppressants to prevent immune destruction of stem cells
colony-stimulating factors to increase WBC count
What is polycythaemia?
increased Hb content and haematocrit, resulting in increased blood viscosity and poor tissue perfusion
Symptoms of polycythaemia
ruddy appearance cyanosis headaches blurred vision hypertension
Causes of aplastic anaemia
primary - changes in bone marrow, stem cell defect
secondary - increased erythropoietin: altitude, smoking, renal, carcinoma
How to treat primary cause of aplastic anaemia?
venesection (bleeding)
radioactive phosphorus - myelosuppression (bone mineralisation, kills off fast growing cells)
cytotoxic agents - myelosuppression
