Microcytic Anaemia

Question 1

what- microcytic anaemia?

Answer 1

-Anaemia caused by deficient haemoglobin synthesis (cytoplasmic defect) causing small RBC

Question 2

what measures size of RBC?

Answer 2

MCV

Question 3

causes- microcytic anaemia?

Answer 3

TAILS

Thalassaemia
Anaemia of chronic disease
Iron deficiency Anaemia (most common)
Lead poisoning
Sideroblastic anaemia

Question 4

most common cause- microcytic anaemia?

Answer 4

iron deficiency

Question 5

describe the pathophysiology of microcytic anaemia

Answer 5

• In microcytic anaemia, one of the building blocks needed to synthesize Hb in the cytoplasm is lacking
  *Hb is made out of haem (require iron) and globin
• However the nuclear machinery is intact, so the cells can keep dividing
• This results in microcytic (small) cells, and as they contain little Hb they are hypochromic (lacking in colour)

Question 6

pathophysiology of anaemia of chronic disease?

Answer 6

It is a protective mechanism to reduce iron supply to pathogens:
-increased release of inflammatory markers, increases production of Hepcidin in liver
-Hepcidin causes degredation of ferroportin, meaning that the iron cannot leave the duodenal enterocyte or macrophage, decreasing ferritin production and so Hb cannot be made
-nuclear machinery still in tact and so the cell continues to divide resulting in microcytic and hypochromic cells

Question 7

Causes of iron deficiency anaemia?

Answer 7

-Blood loss
-Diet
-Poor absorption

Question 8

who is at a greater risk of being iron deficient from diet and why?

Answer 8

-women and children due to greater requirements

Question 9

what may cause bleeding and then iron deficiency?

Answer 9

Chronic blood loss: menorrhgia, GI (tumours, ulcers, NSAID, parasitic infection), haematuria

Question 10

what may cause malabsorption and then lead to iron deficiency?

Answer 10

-Coeliac disease
-Certain medications such as PPIs (because iron requires acid to be absorbed through DMT-1 and into the duodenal enterocytes)

Question 11

where is iron absorbed?

Answer 11

proximal small bowel (duodenum)

Question 12

what may enhance iron absorption?

Answer 12

-ascorbic acid (Vit C)
-alcohol
-haem (from meat) iron is easier to absorb than non haem iron (from vegetables) as there is a direct haem transporter

Question 13

what may inhibit absorption?

Answer 13

-Calcium
-Tannins e.g. tea
-Phytates e.g. cereals, bran, nuts and seeds

Question 14

is haem or non haem iron easier to absorb and why?

Answer 14

haem iron (from meat) is easier to absorb than non haem iron (from beg) as it has a direct haem transporter

Question 15

explain transport of non haem iron (iron from veg)

Answer 15

1. Iron digested and presents in Fe3+
2. Fe3+ converted to Fe2+ by duodenal cytochrome B on the lumen of duodenum
3. Fe2+ and H+ transported into the duodenal enterocyte by DMT-1 (divalent metal transporter 1)
4. Some iron is stored as ferritin
5. Fe2+ leaves the cell through ferroportin
6. Hephaestin converts Fe2+ to Fe3+ (Iron needs to be in Fe3+ form to travel)
7. Transferrin binds to Fe3+ and allows it to travel through the body
8. 75% transferrin goes to bone marrow for erythropoieisis, they bind to tranferrin receptors on RBC, 10-20% taken to the liver and stored as ferritin in the liver

Question 16

Epithelial changes seen in iron deficient anaemia?

Answer 16

-Koilonychia (spoon shaped nails)
-Angular chelitis
-Atrophic glossitis (smooth tongue due to atrophy of papillae)
-Brittle hair and nails

Question 17

Investigations done for microcytic anaemia?

Answer 17

Hb- low
Serum ferritin- low
% saturation of transferring with iron- los

Question 18

what is serum ferritin measuring?

Answer 18

-it is taken from plasma but accurate representation of storage ferritin

Question 19

can someone have normal serum ferritin and still be iron deficient?

Answer 19

yes they can in infection
-serum ferritin is an ACUTE PHASE PROTEIN and so will rise secondary to infection

Question 20

what is sideroblastic anaemia?

Answer 20

A rare blood disorder that causes failure of iron to bind to the porphyrin ring of haem leading to an excess build up in mitochondria of red cell precursors

-there is sufficient iron but ineffective erythropoiesis

Question 21

what can cause sideroblastic anaemia?

Answer 21

Can be hereditary or aquired

Aquired causes:
-Lead poisoning
-MDS
-Alcohol excess

Question 22

what happens if you give someone with sideoblastic anaemia an iron replacement?

Answer 22

Nothing will happen with Sideroblastic anaemia

Question 23

what is seen on blood film of someone with sideroblastic anaemia?

Answer 23

ring sideroblasts in the nucleus

Question 24

what are thalassameias?

Answer 24

diseases that cause reduced globin chain synthesis resulting in impaired haemoglobin production

alpha thalassaemia- alpha chains affected

beta thalassamia- beta chains affected

Question 25

are thalassaemias autosomal dominant or autosomal recessive?

Answer 25

autosomal recessive

Question 26

what are the two main types of thalassamia?

Answer 26

alpha thalassaemia- problem with alpha chain synthesis

beta thalassaemia- problem with beta chain synthesis

Question 27

how can alpha thalassaemia be classified?

Answer 27

-based on the number of alpha genes affected (usually there are 4 normal alpha genes)

Alpha thalassaemia trait- one or two alpha genes missing

HbH disease- only one alpha gene missing

Hb Barts Hydrops- no functional alpha genes