Haemolytic anaemias Flashcards
What is haemolyic anaemia?
Anaemia due to shortened RBC survival.
What is the normal RBC lifecycle?
- 2x1011 RBC/day in bone marrow
- circulates 120 days without nuclei and organelles - survives by cytoplasmic enzymes
- travels 300 miles through microcirculation as small as 3.5 microns, RBC diameter is 8 microns but is able to deform
- senescent RBC removed from circulation by reticular endothelial system of liver and spleen
What is haemolysis? What occurs as a result?
Shortened red cell survival, 30-80 days from 120
Bone marrow compensates by increasing production of RBC
Causes increased young cells in circulation, reticulocytosis (increased reticulocytes) and nucleated RBC
What happens in incompletely compensated haemolysis?
RBC production can’t keep up with decreased RBC lifespan
Leads to decreased Hb
(if RBC could keep up then there would be compensated haemolysis and Hb levels stay normal)
What are the clinical findings from haemolysis?
Jaundice – RBC broken down, Hb is broken down to heme and globin. Heme broken down to iron, which is then broken down to bilirubin. Increased unconjugated bilirubin in plasma – gives rise to jaundice
Pallor - because of low level of hb
Fatigue
Splenomegaly – spleen enlarges
What are the chronic clinical findingds of haemolysis?
Gallstones – pigment – as a result of bilirubin
Leg ulcers – due to vascular stasis of local ischaemia in that area
Folate deficiency (increased use) to compensate for loss of RBC
What would be seen in a blood film of someone with HA?
- polychromatophilia - red cells that are basophilic in colour (blue) due to increased number of reticulocytes (immature RBC)
- nucleated RBC
- thrombocytosis (increased platelets)
- neutrophilia with left shift
What morphological abnormalities to RBC might you see in someone with HA?
- Spherocytes
- Sickle cell
- Target cells
- Schistocytes (fragmented, triangular rbc)
- Acanthocytes
In BM there is compensatory mechanisms to haemolysis, what is happening in erthryoid hyperplasia of BM?
- with normoblastic reaction normoblast being formed
- reversal of myeloid: erthyroid ratio – under normal conditions m:e ratio is 4 to 1
- In haemolytic anaemia as a result of erythroid hyerplasia, there is reversal so it is now 1 myeloid: 4 erthyroid
- 1:4
What is the clinical findings for reticulocytes?
Mild reticulocytosis (2-10% reticulocyte increase in bone marrow) seen in haemoglobinopathies
Moderate to marked reticulocytosis (10-60% reticulocytes in bone marrow) seen in:
- IHAs (immune haemolytic anaemia)
- HS (hereditary spherocytosis)
- G6PD def (glucose 6 phosphate dehydrogenase deficiency)
Wha three ways can HA be classified? With examples.
- Inheritance
- Hereditary
- Acquired
Examples: hereditary spherocytosis or IHA/ immune haemolytic anaemia
- Site of RBC destruction
- Intravascular e.g within vascular system
- Extravascular e.g in reticular endothelial system like liver or spleen
Examples: Haemolytic transfusion Rxn or autoimmune haemolysis
- Origin of RBC damage
- Intrinsic (intracorpuscular)
- Extrinisic (Extracorpuscular)
Examples: G6PD deficiency or infections
What three defects can occur in intrinsic intracorpuscular HA?
- Membrane defects
- Hereditary spherocytosis
- Hereditary elliptocytosis
- H.Pyropokilocytosis
- Enzyme defects
- G6PD glucose 6 oyruvate dehydrogenase deficiency
- PK pyruvate kinase deficiency
- Haemoglobin defects
- Sickle cell disease
- Thalassamias
Give examples of what could cause immune mediated extrinsic extracorpuscular HA
Autoimmune causes:
- Warm – immune mediation takes place at high temp at 37 degrees
- Cold – temp between 4-37 degrees
- Drug induced
Alloimmune causes:
- HDN – haemolytic disease of newborn
- Haemolytic transfusion rxn
Give examples of what could cause non-immune mediated extrinsic extracorpuscular HA
Red cell fragmentation syndrome
- Mechanical trauma e.g artificial valve destroying RBC
- Microangiopathic haemolytic anaemia
- to do with destruction of red cell within vascular system caused by fibrin deposited in the vascular endothelial e.g HUS/haemolytic uraemic syndrome, TTP thrombotic thrombocytopenia purpura, DIC disseminated intravascular coagulation
Drugs and chemicals
Infections:
- Malaria, clostridium
March haemoglobinuria – haemolysis occurs after marching or running on hard surfaces
Hypersplenism
- in red those that occur intravascularly as well
What are the steps through the normal destruction of RBC?
- Occurs in reticular endothelial system (extravascular)
- RBC engulfed via macrophages within reticular system
- RBC broken down to globin, iron, protoporphyrin
- iron and globin reused for synthesis of Hb
- Protophoryin broken into bilirubin, transported from RES to liver as unconjugated bilirubin
- Conjugated in liver
- Enters small intestine through circulatory system
- Excreted as stercobilinogen (faeces)
- Or excreted in urine as urobilinogen
What are the steps through the abnormal destruction of RBC?
- In vacular system (intravascular)
- haemolysis leads to release of Hb
- absorbed back into circulation
- some goes to kidney, excreted in urine
- in urine can find haemoglobinuria
- breakdown of Hb gives pigment, haemosiderin, also found in urine - haemosiderinuria
What is the red cell membrane made up of? What proteins does it contain?
- Lipid bilayer which has integral peripheral proteins that travels across the lipid bilayer
- lipid bilayer has phospholipid on the outer and inner side of the membrane
- Protein band 3 is integral peripheral protein
- Glycophorin A and C are also peripheral proteins
- Cytoskeleton proteins include alpha and beta spectrin, ankyrin, protein 4.2, protein 4.1 and actin
What is hereditary spheocytosis? What causes it?
Hereditary spherocytosis is the most common red cell membrane defect amongst nothern europeans.
Autosomal dominant condition, caused by defects in vertical interactions.
Defects in the spectrin and ankyrin, and protein 4.2.
What is hereditary elliptocytosis? What causes it?
Hereditary elliptocytosis is due to defects in horizontal interactions
e.g mutations in alpha spectrin or beta spectrin
or due to loss of interaction between ankyrin and spectrin
deficiency in protein 4.1 can also be a cause of hereditary elliptocytosis.
What features are seen on a blood film for hereditary spherocytosis?
- Micro spherocytes, cells are spherical in shape and deeply stained with no central pallor
- Polychromatic cells due to increase in RNA in the cells
- Because of defect in membrane cytoskeletal proteins, as cells go through reticular endothelial system and back are not able to retain their biconcave shape and become spherical, become less deformable, have increased risk of haemolysis
What features are seen on a blood film for hereditary elliptocytes?
- Elliptocytes look like teardrops
- Elongated red cells with no pointed ends
What are the clinical features of hereditary spherocytosis?
- Asymptomatic to severe haemolysis
- Neonatal jaundice
- Splenomegaly – spleen removing damaged red cells, spleen becomes enlarged
- Pigment gallstones – because of breakdown of rbc, more bilirubin is produced, causing this – bilirubin forms gallstones in the gallbladder
- Reduced eosin-5-maleimide (EMA) binding – binds to band 3 – test for hereditary spherocytosis, a flow cytometry test widely used to detect hereditary spherocytosis.
- Positive family history as it is autosomal dominant condition
- Negative direct antibody test
What is the role of the hexose monophosphase shunt?
G6P is converted to 6 phosphogluconate by glucose 6 phosphate dehydrogenase
generates NADPH which converts oxidised glutathione to reduced glutathione – this is important as it is an antioxidant
GSH protects the cell and Hb within RBC from oxidative stress
What effect does glucose 6 phosphate deydrogenase deficiency have on Hb?
Oxidative stress
Oxidation of Hb by oxidant radicals.
- Resulting denatured Hb aggregates and forms Heinz bodies - bind to membrane
Oxidised membrane proteins
- Reduced RBC deformability, can’t deform and come back to normal form
What does the glycolytic pathway generate?
Generates energy in ATP;
- To maintain red cell shape and deformability
- To regulate intracellular cation conc. Via cation pumps (Na/K pump) - pumps 3 Na+ out and 2 K+ in.
What does pyruvate kinase deficiency result in?
(Autosomal recessive disorder)
Deficiency in PK affects intracellular cation pumps, more potassium leaves cells, cells become dehydrated and can lyse easily.
- Low ATP generation
On blood film:
- Prickle cells, pricks on the cell membrane
- Some cells have bigger halo, so have less Hb inside
Non-spherocytic haemolytic anaemia
Thalassaemia is a heterogenous group of genetic disorders of Hb synthesis, what can it lead to?
- Imbalanced alpha and beta chain production
- Causes excess unpaired globin chains, making Hb or RBC unstable.
- If there is reduced synthesis of one of the globin chains, one will be overproduced, causing excess in the cytoplasm of the red cell.
- This can cause Ineffective erythropoiesis
What is thalassemia clinically divided into?
Hydrop foetalis
B-thalassaemia major
Thalassaemia intermedia
Thalassaemia minor
What are the clinical features of B thalassaemia major (B0/B0, absence of both beta globin chains)?
Severe anaemia, 3-6 months after birth
Progressive hepatosplenomegaly – spleen and liver enlargement
Bone marrow expansion – facial bone abnormalities due to extensive erythroid hyperplasia
Mild jaundice
Iron overload
Intermittent infections, pallor (paleness) – as a result of anaemia, spleen removal can also cause this
Iron overload – condition is transfusion dependent, transfusion can lead to iron overload and affect some of the organs in the body, particularly endocrine organs
What is seen in the peripheral blood of someone with B thalassaemia major?
Microcytic hypochromic RBC with decreased MCV, MCH, MCHC
Anisopoikilocytosis; target cells, nucleated RBC, tear drop cells
Reticulocytes increase >2%
What are the clinical features of B-thalassaemia trait (minor)?
Asymptomatic
Often confused with Fe deficiency
Need to sometimes exclude a-thalassaemia trait
HbA2 increased in B-thal trait (diagnostic). Seen in haemoglobin electrophoresis and use this to diagnose it
Band for A2 is almost the same as B thalassaemia major.
What is Hb barts hydrops syndrome? (Alpha (a) thalassaemia)
Deletion of all 4 globin genes
Incompatible with life because the alpha globin gene is required for fetal and adult Hb, fetus normally dies in utero or immediately after birth .
What is HbH disease? What are the clinical features?
- Deletion of ¾ a-globin genes
- Common in SE asia
Clinical features:
Moderate chronic haemolytic anaemia, Hb between 7-11 g/dl
Splenomegaly, hepatomegaly – enlargement of spleen and sometimes of liver seen
Hypochromic microcytic anaemia, poikilocytosis, polychromasia, target cells
Electrophoresis – diagnostic , in order to diagnose this and see the HbH band
What is thalassaemia trait (minor) (- a/aa) (- a/- a) (- -/aa) ?
Deletion of one or two of the alpha globin genes
Normal or mild haemolytic anaemia
MCV and MCH is low
What is thalassaemia intermedia?
Group of disorders with mild to moderate anaemia, Hb between 7-10g/dl.
Manifestation too severe to be classified as minor, too mild to be major.
What are the clinical features of thalassaemia intermedia?
Disorder is Transfusion independent
There is diverse clinical phenotype
Varying symptoms – anaemia, jaundice, splenomegaly
Symptoms between beta thalassaemia major and minor
Increased bilirubin level
Diagnosis – is largely based on clinical symptoms
What is seen in the blood film of a thalassemia patient?
Can see nucleated RBC
Poikilocytosis, cells are of different shapes and sizes (anisocytosis)
Hypochromia, pale
Target cells
What causes sickle cell disease?
SCD – refers to all diseases as a result of inherited HbS
Point mutation on 6th amino acid which is glutamic acid that changes the adenine to a thymine, glutamic acid is changed to valine that makes HbS.
Change makes HbS insoluble when it is deoxygenated. As a result HbS polymerises and forms sickle cell shape.
- HbSS is sickle cell anaemia (homozygous state)
- HbAS – sickle cell trait (heterozygous)
What causes oxidative damage and Hb sickling?
Blood travels to deliver oxygent, repeatedly alternating deoxygenated and oxygenated states leading to membrane distortion.
What are the clinical features of SCD?
- Painful cries, due to infarct causing severe pain in bones, particularly shoulders and hips
- Aplastic crises , due to infection with parvo virus
- Infections due to hyposplenism , splenic sequestration which occurs from cyclin and infarction with speel
- Acute sickling which leads to:
- Chest syndrome, due to occlusion of pulmonary vasculature
- Splenic sequestration
- Stroke
Chronic sickling effects which can lead to:
- Renal failure
- Avascular necrosis bone
What are the clinical findings of SCD?
Anaemia
- Hb often between 60-90 g/dl
Reticulocytosis (increase)
Increased NRBC, nucleated red blood cells in peripheral blood
Raised bilirubin because RBC are being broken down much quicker or being destroyed
Low creatinine
What tests are used to confirm a diagnosis of SCA?
Solubility test based on
- Exposing red blood cells to reducing agent. Have a positive and negative control. Positive control contains HbS , negative control contains HbA
- HbS precipitated
- Positive trait and disease
- clouded = HbS
HPLC, high performance liquid chromatography or haemoglobin electrophoresis. You can compare the profiles to normal profile
Hb electrophoresis to see HbSS.
