Session 4 anaemias Flashcards
Why are RBC’s in megaloblastic anaemia so big?
Cytoplasm develops before nuclear maturation and cell division occur
(lots of cytoplasm, large nuclei and open chromatin)
In femtolitres, how big is an RBC in macrocytic anaemia?
> 100 fl
normal: 80-100 fl
What neurological symptoms can a B12 deficiency cause?
dementia, depression
Where are the spleen and liver in abdomen?
Liver - upper right
Spleen - upper left
Which system removes old red blood cells?
Which particular organ of this system?
Reticuloendothelial system
spleen
Where does extramedullary haematopoiesis take place?
liver > hepatomegaly
spleen > splenomegaly
bone cortex > skeletal deformities
Why is bilirubin high in haemolytic anaemia?
Spleen removes RBC’s
metabolises haem to bilirubin
What is myelofibrosis?
How can you diagnose it?
Condition where fat cells for the bone marrow are replaced by fibrotic tissue (less haematopoiesis)
Tear shaped RBC’s
Splenomegaly (extramedullay haematopoiesis)
Why is there raised lactate dehydrogenase in haemolytic anaemia?
Enzyme in RBC’s released when they lyse
interconverts between pyruvate and lactate
Intravascular vs extravascular haemolytic anameia?
intra- in vessels
extra- RES (in spleen or liver by macrophages)
Which proteins are deficient in hereditary spherocytosis?
ankyrin / protein 4.2
Which mutation occurs in sickle cell anaemia?
glutamate to valine on beta chain of haemoglobin
How do sickle cell RBC’s behave in deoxygenated conditions?
When is this exacerbated?
polymerise irreversibly (occlude vessels > MI/ stroke)
cold and infection
What are thalassemias?
Reduced rate of alpha/ beta chain synthesis in haemoglobin
Hb A - x2 alpha chains, x2 beta chains
Give 4 causes of macrocytic anaemias?
- B12/ folate deficiency
- alcoholism (folate deficiency)
- liver disease (less B12/ folate storage)
- reticulocytosis
3 causes of microcytic anaemias?
Why are the cells so small?
Iron deficiency
Anaemia of chronic disease (sometimes)
Thalassaemia
Reduced rate of haemoglobin synthesis
What is sideroblastic anaemia?
type of microcytic anaemia
inherited defects in haem synthesis pathway
How does lead poisoning cause microcytic anaemia?
Inhibits enzymes in the haem synthesis pathway
In what form is iron absorbed?
Ferrous, Fe2+ (more readily available in haem iron)
Why is free iron toxic to cells?
Catalyses reactions which produce ROS
How is haem iron absorbed from the duodenum?
Haem iron (fe2+) transported in to the enterocyte
Haem oxidase degrades haem to release the free ferrous iron
Transported into the blood via ferroportin
Binds transferrin as FE3+
How is non-haem iron absorbed from the intestine?
Ferric (Fe3+) reduced to Fe2+ by DcytB (duodenal cytochrome B)
Fe2+ carried into the cell by DMT1 (divalent metal transporter 1)
Which liver peptide is the main regulator of iron absorption?
Hepcidin
- Binds ferroportin causing its degradation
- inhibits transcription of DMT1
Which foods, vitamins and drugs affect iron absorption?
Tannins (tea) and phylates (chapattis and pulses) inhibit iron absorption bu binding non-haem iron
Antacids inhibit iron absorption
Vitamin C aids iron absorption
(helps reduce fe3+ to fe2+)
