Microcytic Anaemia & Iron Deficiency Flashcards
Where is haemoglobin synthesised
In the cytoplasm of red cell precursors
What are the building blocks for Hb
Iron, porphyrin ring, globins
Pathophysiology of microcytic anaemia
- lack of iron or porphyrin ring or globins
- unable to synthesis Hb
- as nucleus is intact, cells keep dividing
- signal to stop dividing (Hb accumulation) is delayed
- cell division occurs in excess
- smaller cells & little Hb
(Microcytic) (Hypochromic) - hypochromic, microcytic anaemia
What does a hypochromic, microcytic anaemia indicate
Deficient haemoglobin synthesis:
a cytoplasmic defect
Hypochromic microcytic anaemia aetiology
T - Thalassaemia
A - Anaemia of chronic disease
I - Iron deficiency (most common)
L - Lead poising
S - (congenital) sideroblastic anaemia
Globin deficiency - T
Haem iron deficiency - A & I
Haem porphyrin synthesis deficiency - L & S
Iron functions & dangers
- required for oxygen transport (Hb & myglobin)
- required for electron transport
- potentially toxic - can generate free radicals (& so needs a chaperone molecule)
What molecule does circulating iron bind to? Where does it travel to?
- Circulating iron is bound to TRANSFERRIN.
- It is transferred to the bone marrow MACROPHAGES that regulate iron uptake by transferrin receptor expression
- They ‘feed’ iron to RED CELL PRECURSORS
Where is iron stored and in what form is it stored as?
Iron is stored as FERRITIN mainly in the LIVER
What tests can be carried out to assess iron status
● Functional iron
−Haemoglobin
● Transported iron
−Serum iron
−Transferrin
−Transferrin saturation
● Storage iron
−Serum ferritin
What is transferrin and what is its function?
A protein with two binding sites for iron that transports its from donor tissues to tissues expressing transferrin receptors
Donor tissues - intestinal cells, macrophages, hepatocytes
Tissue expressing transferrin receptors - above & ERYTHROID MARROW CELLS i.e. RBC PRECURSORS
% saturation of transferrin with iron is a measure of iron supply. Name two causes of reduced saturation and one cause of increased saturation.
– reduced in iron deficiency
– reduced in anaemia of chronic disease
– increased in genetic haemachromatosis
NOTE - low transferrin does not mean iron deficiency
What is ferritin and what is its function?
Intracellular protein that stores up to 4000 Fe3+ ions.
Mainly found in liver,
Tiny amounts in other tissues, macrophages & serum
What does serum ferritin indicate
Serum ferritin indirectly reflects iron storage
What two tests can confirm iron deficiency
- Microcytic anaemia (decreased functional iron) &
- Reduced storage iron (low serum ferritin)
NOT - Reduced transport iron (low serum transferrin)
Iron deficiency aetiology
C - Coeliac disease (Fe absorbed in proximal small bowel)
A - Achlorhydria/ Anti-acids (Non-haem Fe absorption requires acidic env)
V - Vegetarians (lack of Fe in diet)
E - Excess blood/iron loss (GI bleed/ heavy menstrual bleed/ haematuria)
Iron deficiency (microcytic anaemia) treatment
1) Treat cause (definitive)
- review diet
- review meds e.g. anti-coagulants, PPIs
- coeliac/ menorrhagia/ malignancy etc treatment
2) Iron supplements (symptomatic)
Iron deficiency (microcytic anaemia) treatment monitoring & findings
What should you expect
- Rise in Hb concentration, reticulocytes & MCV (4-6 weeks)
- Rise in ferritin (once Hb returns to normal) (2-3 months)
If improvement does not occur
- check compliance
- check the ability of bone marrow to up regulate RBCs
- check if the cause of iron deficiency is still present
Name some signs of chronic lack of iron/ longstanding iron deficiency anaemia
- Pruiritis
- Koilonychia & brittle nails
- Brittle hair
- Angular stomatitis
What is sideroblastic anaemia
Excess iron build up in mitochondria (blue granules around nucleus) due to failure to incorporate iron in to haem.
Can be hereditary or acquired eg MDS, lead poisoning, alcohol excess
Iron deficiency screening tests to work out aetiology
GI investigations (even without symptoms) => bleeding
Coeliac screen (all) => coeliac
Review drugs => PPIs, H2RA etc
Review diet => haem (meat) & non heam (veg.)
Why can serum ferritin be raised despite iron deficiency
Ferritin is an acute phase protein and so can be raised in acute inflammation
What molecule competes with iron absorption in the proximal small bowel
Calcium
What is the difference between absolute and functional iron deficiency
Absolute - True lack of iron
Functional - Sufficient iron but can’t use it properly e.g. AOCD
