intro to anaemia and microcytic anaemia Flashcards
what is the definition of anaemia?
reduced total red cell mass
use Hb as a substitute to measure this
male Hb <130g/l
Female Hb <120g/l
where does red cell production occur?
in BM
How is Hb measured?
Lyse Red cells to create a Hb solution
stabilise the Hb molecules and then measure the optical density, the optical density is proportional to the concentration
Hb concentration then calculated against standard solution
What is the haematocrit?
Ratio of the whole blood that is red cells if sample left to settle
When might Hb and haematocrit levels be a poor marker for anaemia?
if there is a rapid bleed and loss of blood volume and then plasma re-expansion i.e. haemodilaution
how does the body respond to anaemia?
increased production of reticulocytes
what are reticulocytes?
- size?
- content?
- appearance on stain?
red cells that have just left the BM
- larger than average RBC
- still have RNA
- stain purple and on blood film appear polychromatic
name the RBC components of a full blood count?
-other investigations (2)
Hb conc No. of cells Mean cell volume i.e. size Haematocrit Mean cell haemoglobin (MCH) Mean cell haemoglobin Conc (MCC)
-blood film
reticulocyte count
Classification of anaemia
-name the 2 ways in which we classify anaemia?
By pathophysiology
by morphological characteristics
Pathophysiological classification of anaemia
- state the 2 reasons for this kind of anaemia and the change to relic count seen?
- give 2 reasons why these might occur
-decreased production (low relic count)
increases loss or destruction of red cells(high relic count)
-Dec production Hypo proliferative (reduced erythropoiesis) maturation abnormality (erythropoiesis present but ineffective due to cytoplasmic or nuclear defects)
In destruction/loss
bleeding
Haemolysis
In abnormal maturation of RBCs, state what change to MCV is seen:
- nuclear defects
- cytoplasmic defects
- high, big cells i.e. macrocytic
- low, small cells i.e. microcytic
Microcytic anaemia
- where is Hb synthesised?
- what components of Hb are needed for its synthesis?
- shortage of these components means what?
- Hb synthesised in the cytoplasm
- Hb needs Globins, haem, porphyrn ring and Iron
-shortage of these results in small RBCs with a low Hb content
= microcytic & hypochromic
Causes of hypochromic microcytic anaemias
- Haem deficiency, give causes (3)
- Globin deficiency, give cause (1)
-lack of Iron for erythropoiesis
(iron def, anaemia of chronic disease)
Problems with porforin synthesis
(lead poisoning/ peroxiding responsive anaemias)
Congenital sideroblastic anaemia
-Thalassaemia
(trait, intermedia, major)
Iron
- can exist in what 2 states?
- required for what in the body? (2)
- generates what toxic components?
-Fe2+ or Fe3+
-O2 transport (for Hb, myoglobin) Electron transport (mitochondrial production of ATP)
-free radicals so needs to be handled safely by body
Adult haemoglobin
- describe the structure?
- how many O2 molecules can 1 haem group bind?
-4 global subunits with single haem molecule
haem group contains single Fe2+ ion
each haem group can bind one O2 molecule
Iron metabolism
- describe the system for Iron use in the body?
- how much is excreted daily and where is Iron stored?
- circulating iron binds to what?
- how does iron get incorporated into RBCs
- another storage method for iron?
-closed system
-only absorb and excrete small amounts
tiny amount in circulation
most in storage in BM
- circulation iron bound to transferrin
- it is transferred to bone marrow macrophages that feed it to red cell precursors
- ferritin, stored in the liver
whats used to asses iron status?
- functional iron?
- Transported Iron?
- Storage Iron?
-Haemoglobin
-serum iron
transferrin
transferrin saturation
-Serum ferritin
Transferrin
- what is it?
- function?
- reduced in?
- increased in?
- protein with 2 binding sites for iron atoms
- transports iron from donor tissues to tissue expressing transferrin receptor (erythroid marrow)
-Iron def
anaemia of chronic disease
-genetic haemachromatosis
Ferritin
- what is it?
- function?
- measures what?
- reduced in?
- Large intercellular protein
- spherical and stores up to 4000 ferric ions, tiny amounts present in serum
- reflects intracellular ferritin synthesis in response to iron status of the host so indirect measure of storage iron
- iron def
Causes of iron deficiency
give the 3 main reasons
-dietary deficiency
relative (to needs) and absolute (veggie)
blood loss
e.g. GI
malabsorption
coeliac disease
achlorhydria
Chronic blood loss
-causes? (3)
-Menorrhagia (can lose 30-40ml/month which is 15-20mg/month)
GI (tumours, ulcers, NSAIDs)
Haematuria
what are the sequential consequences of negative iron balance physiologically?
- Iron stores exhausted
- iron deficient erythropoiesis
- Microcytic anaemia
- epithelial changes (skin, koilonychia)
Iron deficiency is NOT A DIAGNOSIS, SEARCH FOR UNDERLYING PROBLEM!!
FIND THE BLEED OR THE CANCER OR WHATEVER!!
