Iron Deficiency Anaemia Flashcards
What is needed for normal RBC production?
- Drive for erythropoiesis (the hormone erythropoietin, released by kidney),
- ‘Recipe’ for erythropoiesis (genes),
- ‘Ingredients’ (Iron, B12, Folate and minerals),
- Functioning bone marrow
What is the composition of haemoglobin (delete)
- 4 globin chains (2 beta and 2 alpha),
- 4 Haem groups (one per chain)
What is the composition of haem? (delete)
Consists of a proto-porphyrin bound to an iron ion
What is the total body iron and where is it stored? (delete)
Total - 4G. It is stored in; Bone marrow and RBCs, reticuloendothelial system, myoglobin and enzymes
How is iron transported in the plasma? delete
Bound to the glycoprotein called transferrin. It is produced by hepatocytes in response to iron levels in the body (low iron, increased production of transferrin). It has two iron binding domains
Explain how iron is transferred to erythrocytes (RBCs)
Transferrin will bind to transferrin receptors on the surfaces of erythrocytes. The erythrocytes take up the iron and either send it to the mitochondria where it will produce haem of store the iron as ferritin.
What is the reticuloendothelial system?
It is comprised of cells decending from monocytes that are able to phagocytose materials. 90% exists in the liver
Explain the reticuloendothelial system’s storage of iron
Macrophages phagocytose old red blood cells (around their 120 day life span), Hemosiderin then stores the ferritin in the macrophages. Serum ferritin approximates the RES iron.
1mmol/l of serum ferritin = how much RES iron and what is the issue with using this as a method of measuring RES iron? delete
8mg of RES iron. However, Serum ferritin is an acute phase protein so will appear raised in time of inflammation or tissue damage
What is the daily iron intake needs?
1-2mg per day
Explain the absorption of iron
Mainly occurring in the duodenum, iron crosses the cell membrane via the DMT1 channel into the enterocyte. It can then cross into the plasma via the ferroporin channel (regulated by hepcidin)
What prevents the absorption of iron?
Hepcidin. It binds to ferroportin and degrades it, reducing iron absorption and decreasing iron release from RES. This is the only way of regulating iron in the body as there is no method of excretion
What is the molecular basis of hereditary haemochromatosis?
Loss of hepcidin so cannot prevent absorption of iron
What are some causes of hypochromic microcytic red blood cells
- Iron def anaemia,
- Thalassaemia,
- Anaemia of chronic disease,
- Sideroblastic anaemia
Describe the development of IDA
Initially, Hb will remain normal despite low serum ferritin and low RES iron stores. This is called latent iron deficiency. Overtime this will progress and Hb will fall. Therefore IDA is gradual
What are the symptoms of iron deficiency anaemia
- Palor, tachycardia, rapid breathing, peripheral oedema (if severe),
- Koilonychia, hair loss, pica, atrophic glossitis, angular stomatitis, oesophageal web
What is an oesophageal web?
A thin mucous membrane that forms across the upper part of the oesophagus which causes dysphagia.
What is a silent GI cause of iron def anaemia?
Cecal carcinoma. Since right sides GI carcinomas don’t cause strictures then they don’t tend to present GI symptoms
What is the main treatment for iron def anaemia?
First, must discover the underlying cause!!
1. Ferrous sulphate 200mg = 60mg essential iron.
2. If ferrous sulphate experiances GI upset then can use ferrous gluconate 300mg = 36mg essential iron
What are the indications of delivering iron intravenously?
- Intolerance of oral iron,
- Compliance,
- Renal anaemia and Epo replacement.
Give 1G over 2-3 hours. However the Hb rises no faster than with oral iron.
How will anaemia of renal failure present?
Anaemia of chronic disease and reduce Epo
What will be the likely lab values in a patient with anaemia of chronic disease?
- Normo/hypo-chromic normo/microcytis RBCs,
- Raised ESR which will give RBC rouleaux,
- Normal/raised ferritin,
- Reduced iron,
- Reduced transferrin
What are the causes of anaemia of chronic disease?
- RES iron blockade (iron trapped in macrophages and raised hepcidin levels.
- Reduced Epo response,
- Depressed marrow activity (cytokine marrow depression)
Where is iron absorbed?
Duodenum and jejunum. It requires acid from the stomach to make insoluble ferric into soluble ferrous. Therefore drugs such as PPIs can affect iron absorption. SO can conditions that cause inflammation of the small bowel (crohns or coeliacs)
What are the causes of iron deficiency anaemia?
- Blood loss (most common cause in adults)
- Dietary insufficiency (children)
- Poor iron absorption (PPIs, coeliac’s or Crohn’s)
- Increased requirement in pregnancy
What are the investigations for iron deficiency anaemia?
Transferrin saturation - Carrier protein for ferric ions.
Total iron binding capacity - Total space on the transferrin molecules for iron to bind.
Serum ferritin - However is an acute phase reactant and can be raised in infection or cancer
Blood film - Hypochromic, microcytic red cells with pencil and target cells
What is the management of iron def anaemia?
- Identify cause - If unknown then do OGD and colonoscopy
- Blood transfusion if Hb around 70.
- Oral iron eg, ferrous sulphate
- If oral is not tolerated or the cause is malabsorption then iron infusion
What are the side effects of oral iron?
Constipation and black coloured stools.
