Session 5-Anaemia, Vit B12 And Folate Flashcards
Why might anaemia develop?
Inability of body to deliver oxygen to tissues-either because not enough RBCs or not enough haemoglobin in RBCs
Where does erythropoiesis occur?
Bone marrow
Which system is involved in the removal of RBCs?
Reticulo-endothelial system
What can lead to reduced erythropoiesis? (2)
1) empty bone marrow - unable to respond to stimulus from erythropoietin
2) marrow infiltrated by cancer cells or fibrous tissue so normal haemopoietic cells are reduced
What happens in chronic kidney disease?
Kidney stops making erythropoietin
In which conditions can anaemia of chronic disease (ACD) be seen?
- Rheumatoid arthritis
- Inflammatory bowel disease (ulcerative colitis or Crohn’s)
- Chronic infection eg TB
- Bronchiectasis (widening of bronchi)
What are the features of anaemia of chronic disease?
1) iron stored in macrophages not released for use in bone marrow
2) circulating RBCs have reduced lifespan
3) marrow shows lack of response to erythropoietin
4) anaemia may be microcytic, normocytic or macrocytic
What are the clinical signs of anaemia of chronic disease?
Increased CRP and ferritin
What happens in myelodysplastic syndromes?
Production of abnormal clones of marrow stem cells - RBCs are large and defective so prematurely destroyed by reticuloendothelial system
What can myelodysplastic syndromes lead to?
Progressive anaemia or pancytopenia
Acute leukaemia
How are myelodysplastic syndromes treated?
Chronic transfusion of RBCs
How can haemoglobin abnormalities lead to anaemia? (3)
1) lack of iron
2) deficiency in building blocks for DNA synthesis
3) mutations in genes that encode globin proteins
What type of anaemia does vitamin B12/folate deficiency lead to?
Megaloblastic anaemia
Complete the sentences:
Humans acquire vitamin B12 by eating foods of _________ origin, leading to excess of B12 in diet of _____ eaters. B12 is combined with glycoprotein ___________ ________ (IF) produced by ____________ cells in stomach. IF-B12 complex binds in _______, leading to absorption of B12 and destruction of IF. In portal blood, B12 is bound to plasma protein ________________ which delivers B12 to bone marrow and other tissues.
Animal Meat Intrinsic factor Parietal Ileum Transcobalamin
What can a deficiency of B12 result from?
1) dietary deficiency
2) intrinsic factor (IF) - Pernicious anaemia
3) IF-B12 complex - disease of terminal ileum
4) transcobalamin deficiency
What is Pernicious anaemia?
Autoimmune disease affecting gastric parietal cells causing lack of intrinsic factor
Which foods are rich in folate?
Most foods: yeast, liver and leafy greens especially
Where does folate absorption occur?
Duodenum and jejunum
What are dietary folates converted to and what is it needed for?
Methyltetrahydrofolate (methylTHF) for DNA synthesis
Why can folate deficiency occur?
Dietary deficiency Proximal small bowel disease eg coeliac disease Crohn's disease drugs Alcoholism Increased use eg pregnancy
How do drugs lead to folate deficiency?
Dihydrofolate reductase enzyme eg Methotrexate leads to reduced methylTHF production
What disease is vitamin B12 deficiency associated with and how does it do this?
Neurological disease
Focal demyelination affecting spinal cord, peripheral nerves and optic nerves (depression and dementia can also develop)
What is thalassaemia?
Reduced rate of synthesis of normal alpha or beta globin chains
What is sickle cell disease?
Synthesis of abnormal haemoglobin
