Iron Deficiency Anaemia Flashcards
What type of anaemia is iron deficiency anaemia?
Microcytic anaemia
Microcytic anaemia => presence of small, often hypochromic RBC in a peripheral blood smear + is usually characterized by a low MCV
What is the most common cause of anaemia?
Iron deficiency anaemia because:
=> limited ability to absorb iron in the body
=> frequent loss of iron due to bleeding
Daily diet intake or iron = 15-20mg but only 10% is absorbed.
Absorption may be increased 20-30% in iron deficiency, growth and pregnancy.
- What are non-haem and haem iron derived from? Which is better for absorption?
- What are the two different forms of iron? Which is better absorbed?
Non-haem iron derived from: fortified cereals
Haem iron derived from: haemoglobin & myoglobin in red or organ meats
=> Haem iron is better absorbed than non-haem
Iron is found in [insoluble] ferric (Fe3+) and ferrous (Fe2+) forms.
=> Ferrous form is more readily absorbed
Where in the small intestine is haem absorbed?
Proximal intestine via the intestinal haem transporter (HCP1) - highly expressed in duodenum
HCP1 is upregulated via iron deficiency and hypoxia
What factors influence iron absorption?
=> Haem iron is absorbed better than non-haem iron
=> Ferrous iron is absorbed better than ferric iron
=> Gastric acidity helps keep iron in the ferrous state and soluble in the upper gut
=> Iron absorption is increased with low iron stores and increased erythropoietic activity i.e. bleeding, haemolysis, high altitude
=> Absorption is decreased in iron overload
How is iron transported in blood?
Iron is transported in the plasma bound to transferrin (beta globulin - synthesised in the liver)
Each transferrin molecule binds 2 atoms of ferric iron
Most of the iron bound to transferrin come from macrophages from the reticuloendothelial system and not from iron absorbed by the intestine.
Macrophages from the reticuloendothelial system recycle the iron from the senescent red blood cells when haemoglobin is broken down
How is iron stored in blood?
2/3 of body iron is in circulation as haemoglobin.
1/3 is stored in reticuloendothelial cells, hepatocytes and skeletal muscle cells.
=> 2/3 of the stored iron is stored as ferritin and 1/3 as haemosiderin
- Ferritin = water soluble iron protein, easily mobilised than haemosiderin for haemoglobin formation
- Haemosiderin = insoluble iron protein found in macrophages in the bone marrow, liver, spleen
What are our daily iron requirements?
Normal serum iron level = 13-32umol/L
=> diurnal rhythm with higher levels in the morning
=> menstruating women lose 30-40mL of blood / month
Excess menstruating blood >100mL / month => iron deficiency anaemia
What causes iron deficiency anaemia?
Iron deficiency anaemia develops if there is inadequate iron for haemoglobin synthesis.
Causes:
=> Blood loss i.e. menorrhagia or GI bleed
=> Increased demands i.e. growth & pregnancy
=> Malabsorption i.e. coeliac’s, post-gastrectomy
=> Poor intake
=> In the tropics, hookworms infections (GI blood loss) => most common cause
What are the clinical features of iron deficiency anaemia?
Symptoms:
=> Dyspnoea
=> Fatigue
=> Headaches / faintness
=> Palpitations
=> Pallor of conjunctiva
Signs of iron deficiency anaemia (only seen if chronic):
=> Brittle nails
=> Koilonychia (spoon shaped nails)
=> Atrophy of the papillae on the tongue - atrophic glossitis
=> Angular stomatitis
=> Brittle hair
=> Plummer Vinson - syndrome of dysphagia + glossitis + iron deficiency anaemia (develops as a result of chronic anaemia)
How do you diagnose iron deficiency anaemia?
- Diagnosis based on clinical hx, which should include:
=> dietary intake questions
=> NSAIDs use (in case of GI bleed)
=> blood in stool i.e. haemorrhoids / colon cancer
=> duration of period / clots / numbers of pads or tampons used - Blood count & film
How do you investigate for iron deficiency anaemia?
- Blood film
=> Microcytic (low mean cell volume, MCV)
=> Hypochromic (low mean corpuscular haemoglobin, MCH)
=> Anisocytosis (variation in size)
=> Poikilocytosis (variation in shape)
- Serum iron and iron-binding capacity (transferrin)
=> Serum iron is not helpful for clinical iron status
=> Transferrin status is more accurate in iron deficiency
- Serum ferritin (iron store)
=> In simple iron deficiency, low serum ferritin level confirms diagnosis
=> Ferritin is also an acute phase reactant so it can increase in inflammatory or malignant states, despite iron deficiency => not too reliable
- Serum transferrin (iron store)
=> Transferrin increases in iron deficiency - more accurate than ferritin
- Check coeliac serology in all
=> if negative, refer all males and non-menstruating females for urgent gastroscopy and colonoscopy
- Stool microscopy if relevant travel hx
What are the differential diagnosis for iron deficiency anaemia?
Other anaemias with microcytosis and hypochromic cells:
=> Thalassaemia
=> Sideroblastic (acquired) anaemia
=> Anaemia of chronic disease
How do you treat iron deficiency anaemia?
- Treat the cause.
- Oral iron e.g. ferrous sulphate 200mg/8h
=> Side effects: nausea, abdominal discomfort, diarrhoea, constipation, black stools
=> Hb should rise 10g/L/week
=> Continue 3 months after normal Hb to replenish stores
- IV iron indicated if oral route is impossible or ineffective
* most common reason for iron replacement therapy failure = lack of compliance due to side effects or can be due to continued blood loss, malabsorption, anaemia of chronic disease, incorrect diagnosis i.e. thalassaemia
Interpreting plasma iron studies : Iron deficiency anaemia
Reduced mean cell volume
Reduced serum iron
Raised serum total iron binding capacity (TIBC)
Reduced ferritin
Increased serum transferrin receptors
Iron in marrow absent
Iron in erythroblasts absent
Interpreting plasma iron studies : Iron deficiency anaemia
Reduced mean cell volume
Reduced serum iron
Raised serum total iron binding capacity (TIBC)
Reduced ferritin
Increased serum transferrin receptors
Iron in marrow absent
Iron in erythroblasts absent
