RBC disorders Flashcards
blood composition
55% plasma, 40% cells,
reticulocytes
newly formed red blood cells
haemopoiesis
formation of new blood cells
process of haemopoiesis
starts in yolk sac, then liver and spleen, then bone marrow
extramedulla
outside of the bone marrow
erythropoiesis
formation of red blood cells
what is the earliest cell type in erythropoiesis to recognise?
normoblast
essential dietary constituents of erythropoiesis
iron, vit B12, folic acid
anaemia
deficiency of red blood cells
what are the Three major types of anaemia
- hypochromic microcytic with a low MCV (Fe deficiency)
- normochromic normocytic with a normal MCV
- macrocytic with a high MCV (megaloblastic)
Pathological consequences of anaemia
tissue hypoxia
signs and symptoms of anaemia
fatigue
headaches
faintness
pallor (conjunctiva)
Laboratory investigations for anaemia
decreased RBC count, haemoglobin and packed cell volume. abnormal blood film
blood film features in anaemic samples
− Anisocytosis: variation in size
− Poikilocytosis: variation in shape
− Anisochromasia: variation in haemoglobinisation
causes of anaemia
Suppressed proliferation e.g. aplastic bone marrow Defective maturation e.g. haematinic deficiency increased destruction e.g. haemorrhage, haemolysis increased reticulocytes
Mechanisms of Fe deficiency
- Increased demands
- Chronic blood loss
- Poor diet
- Malabsorption
megaloblasts
erythrocytes with delayed nucleus maturation
how to detect Fe deficiency using microscopy
doesn’t stain as darkly
howell-jolly bodies
nucleated RBCs
causes of Megaloblastic Anaemia
Deficiency of B12 and folate
Abnormal metabolism of B12 and folate
Other defects of DNA synthesis
why is vit B12 and folate importnat?
needed for methylation of uridine into thymine
Associated chronic diseases of anaemia
− Chronic microbial infections (e.g. osteomyelitis)
− Chronic immune disorders (e.g. rheumatoid arthritis)
− Neoplasm (e.g. Hodgkin’s lymphoma, lung carcinoma)
treatment of chronic anaemia
treat underlying condition and give erythropoietin
Aplastic anaemia
pancytopenia with hypocellularity of bone marrow - lacks many other blood cells types as well
Major causes of aplastic anaemia
idiopathic, chemical agents (used in chemotherapy, cytotoxic antibiotics), physical agents, viral infections
signs of aplastic anaemia
− Bruising, bleeding gums and epistaxis
− Mouth infection
Bone marrow examination of aplastic anaemia
hypocellular marrow with increased fat spaces
causes of haemoglobin abnormalities
Mostly caused by single point mutation of subunit
Abnormal globin chain structure
Imbalanced globin chain production
sickle cell disease cause
single base pair mutation (A becomes T meaning Glu becomes Val) that leads to abnormal beta globin chains - inherited HbS variant
cause of Thalassaemias
abnormalities of globin chain (a or b) synthesis
Thalassaemias diagnosed by…
haemoglobin electrophoresis
Red cell enzyme
Glucose-6-phosphate dehydrogenase
G6PD
Glucose-6-phosphate dehydrogenase importance
vital in hexose monophosphate shunt - maintains glutathione in a reduced state to protect against oxidant injury
cause of Glucose-6-phosphate dehydrogenase deficiency
X linked condition that leads to a single amino acid substitution
Glucose-6-phosphate dehydrogenase deficiency laboratory investigations
bite cells and blister cells in blood film, increased bilirubin
bite cells vs blister cells
bite - oxidised, some parts taken away
blister - some parts beginning to repair
