IDA And ACD Flashcards
Describe how the RBC carries out its functions
- CO2 removal occurs by the RBC taking up CO2 and together with carbonic anhydrase forming H+ and bicarbonate (using Hb as a buffer). Bicarbonate is then exchanged for Cl- (chloride shift)
- oxygen delivery can occur because Hb can bind reversibly to O2 without undergoing oxidation or reduction
Describe the RBCs functional shape
Shaped as a biconcave disc
- for maximal deformability (able to bend and fit through small blood capillaries)
- to increase surface area (for maximal gas transfer
What is the role of transferrin and its features?
- transferrin is what iron binds to for transport in the plasma (responsible for iron delivery to all tissues, erythroblasts, hepatocytes and muscle)
- it is a glycoprotein synthesised in hepatocytes (dependent on amount of iron stores in the body)
- has 2 iron binding domains
What is the role of hepcidin?
Controls the amount of iron absorbed in duodenum and released from macrophages in the RES system.
How is iron taken up in erythroblasts?
- erythroblasts have transferrin receptor on its surface which allows iron bound transferrin to be rapidly taken into cell
- either taken to mitochondrion to be converted to haem or stored as ferritin (insoluble)
How is iron taken up by macrophages?
- iron is taken up by macrophages by phagocytosing RBCs which are reaching the end of their life cycle
- haem from RBC is broken into amino acids, in-conjugated bilirubin and iron
- iron is stored in macrophages as ferritin or release to transferrin in the plasma
Describe how hepcidin regulates iron metabolism
- hepcidin (‘low iron’ enzyme) binds to ferroportin causing degradation preventing iron absorption and release from RES
- requires expression of HFE gene
What is the clinical relevance of hepcidin?
In hereditary haemochromatosis there is a mutation to the HFE gene resulting in the loss of hepcidin which is what causes iron overload
Describe the appearance of the cells in IDA
- pale hypochromic and microcytic cells
- cells cannot produce haem
- <15% saturation of iron
- reduced serum ferritin and Hb
What are other causes of hypochromic microcytic RBCs that are not IDA?
- thalassaemia (not enough globin)
- anaemia of chronic disease (can be normocytic and normochromic too)
- sideroblastic anaemia
What is a problem associated with serum ferritin?
It is also an acute phase protein which poses a risk of IDA in times of tissue inflammation
What are the clinical signs of IDA?
- koilonychia
- atrophic glossitis (smooth tongue)
- angular stomatitis
- oesophageal web (Plummer syndrome - web-like membranes in throat causing dysphagia and problems swallowing)
What is the golden rule for patients presenting with IDA?
- IDA in males and post-menopausal females is due to GI blood loss until proven otherwise
- in young women assume to be menstrual/pregnancy related. GI investigations only if in presence of GI symptoms or blood in stools
What is the treatment for IDA?
- iron replacement (if GI upset caused, reduce amount of elemental iron in makeup)
- IV iron replacement (if intolerant, for complaince, for renal anaemia/epo replacement)
- discover and resolve cause
What happens to iron in anaemia of chronic disease?
- failure of utilisation of iron = reduced epo response or insensitivity
- iron trapped in macrophages of RES (raised levels of hepcidin)
- depressed marrow activity (depression caused by cytokines in inflammation, infection, or neoplasia)
