Haemolytic Anaemia Flashcards
What is haemolytic anaemia?
Anaemia due to shortened RBC survival
How long do RBCs circle for?
Approx 120 days
Where are senescent RBCs removed?
Reticular endothelial system (RES )of the liver and spleen
How long do haemolytic anaemia RBCs survive for?
30-80 days (down from 120 days)
What does the shortened red cell survival mean for the blood?
Increased RBC production and increased young cells in circulation → reticulocytosis
What does bone marrow do during haemolysis?
- Bone marrow compensates by increasing its output of red cells 6-8 fold→ increasing the proportion of red cells produced, expanding the volume of active marrow
What is incomplete compensated haemolysis?
When RBC production is unable to keep up with decreased RBC lifespan → decreased haemoglobin
What are the symptoms of haemolytic anaemia?
- Jaundice
- Pallor
- Fatigue
- Splenomegaly
- Gallstones
- Leg ulcers
- Folate deficiency line folate use in RBC production
What would a peripheral blood film show in haemolytic anaemia?
- Polychromatophilia
- Nucleated RBC
- Thrombocytosis
- Neutrophilia with left shift
What happens to the bone marrow in haemolytic anaemias?
Erythroid hyperplasia
What does haemolytic anaemia cause in the bone marrow?
- Increase in unconjugated bilirubin, lactate dehydrogenase, urobilinogen and urinary haemosiderin
- Decrease serum haploglobin protein that binds free haemoglobin
What does erythroid hyperplasia cause?
- Normoblastic reactions
- Reversal of myeloid: erythroid ratio
- Variable reticulocytosis
What are the general classifications of haemolytic anaemia based on?
- Inheritance
- Site of RBC destruction
- Origin of RBC damage
What are the inheritance classifications of haemolytic anaemia?
- Hereditary
- Acquired
What are the site of RBC destruction classifications of haemolytic anaemia?
- Intravascular
- Extravascular
What are the origin of RBC damage classifications of haemolytic anaemia?
- Intrinsic
- Extrinsic
What is an example of hereditary haemolytic anaemia?
- Hereditary spherocytosis
What is an example of acquired haemolytic anaemia?
Paroxysmal nocturnal hemoglobinuria (PNH)
What is an example of intravascular haemolytic anaemia?
Thrombotic Thrombocytopenic Purpura (TTP)
What is an example of extravascular haemolytic anaemia?
Autoimmune haemolysis
What is an example of intrinsic haemolytic anaemia?
G6PD deficiency
What is an example of extrinsic haemolytic anaemia?
Delayed haemolytic transfusion reaction
What are examples of membrane defect intrinsic haemolytic anaemia?
- Hereditary spherocytosis
- elliptocytosis
- pyroporkilocytosis
What are the causes of Intrinsic (Intracorpuscular) Haemolytic anaemia?
- Membrane defects
- Enzyme defects
- Haemoglobin defects
What are examples of enzyme defect intrinsic haemolytic anaemia?
G6PD, PK
What are examples of haemoglobin defect intrinsic haemolytic anaemia?
- Sickle cell
- Thalassaemias
What are examples of immune mediated extrinsic haemolytic anaemia?
- Autoimmune (warm, cold, drug induced)
- Alloimmune (HDN, haemolytic transfusion reaction)
What are examples of non-immune extrinsic haemolytic anaemia?
- Red cell fragmentation syndromes
- Drugs
- Infections
- Hypersplenism
Which of the haemolytic anaemia occur in the vascular system?
- G6PD
- Protein Kinase
- Drug induced autoimmune
- Haemolytic transfusion reaction
- Red cell fragmentation syndromes
- Infections e.g malaria
- March haemoglobinuria
What is the extracellular site of RBC destruction?
- RBCs are engulfed by macrophages in reticuloendothelial system (REM) and broken down to globin, iron and protoporphyrin.
- Globin and iron reused for synthesis of Hb
- Protoporphyrin is broken down to bilirubin and travels to the liver where it is conjugated.
- The conjugated bilirubin goes into small intestine through circulatory system and excreted in the form of Stercobilinogen (in faeces) and via urine in the form of Urobilinogen.
What is the intravascular site of RBC destruction?
- Breakdown of RBCs in the vascular system leaves Hb which gets reabsorbed back into circulation and some goes into the kidney to be excreted in the urine called Haemoglobinuria
- Due to breakdown you also get haemosiderin à haemosiderinuria.
What normally happens when RBCs breakdown?
Macrophages break them down and they go to the liver to be excreted from the kidney
What happens in haemolytic anaemia for RBC breakdown?
RBCs lyse in veins, which leads to haemoglobinurea
What is the cell membrane made up of?
Membrane is made up of a lipid bilayer that has integral peripheral proteins that traverse across
What are the integral proteins normally found in a cell membrane?
- Glycophorin A and C
- Bard 3
What are the cytoskeletal proteins found in the RBC membrane?
- Ankyrin
- Alpha and beta spectrin
- Protein 4.2 and 4.1
- Actin
What type of disease is hereditary spherocytosis?
- Autosomal dominant
What is hereditary spherocytosis caused by?
- Defects in vertical interactions
- Specifically in spectrin, ankyrin and protein 4.2
How is hereditary spherocytosis managed?
- Monitoring
- Folic acid
- Transfusion
- Splenectomy
What do hereditary spherocytotic cells look like on blood film?
- Deeply stained microspherocytes with no central pallor
- Polychromatophilic cells due to increased RNA.
- Membrane defect results in cytoskeleton not retaining biconcave shape.
What causes hereditary elliptocytosis?
- Defects in horizontal interactions
- Mutations on alpha or beta spectrin
- Deficiency of protein 4.1
What do hereditary elliptocytotic cells look like?
Elongated RBCs with no pointy ends
What are the clinical features of hereditary spherocytosis?
- Asymptomatic until severe haemolysis
- Neonatal jaundice
- Splenomegaly
- Pigment gallstones
What tests for hereditary spherocytosis?
Flow cytometry showing reduced eosin-5-maleimide binding
What is the role of the HMP shunt in the pentose phosphate pathway?
- Generates NADPH and reduced gluthathione
- Protects the cell from oxidative stress
What genetic type of disease is a glucose-6-phosphate dehydrogenase deficiency?
X-linked
What is the cell morphology in G6P dehydrogenase deficiency?
- Bite cells
- Blister cells and ghost cells
- Heinz bodies
What is the role of glucose-6-phosphate dehydrogenase?
- Glucose-6-phosphate is metabolised to 6-phosphogluconate by glucose-6-phosphate dehydrogenase.
- NADPH is produced in the process which converts oxidised glutathione to a reduced form
Why is Reduced glutathione important?
- Reduced glutathione (GSH) is an important antioxidant that protects RBC membrane and Hb in red cell from oxidative stress,
- If GSH not available, this can result in RBC being exposed to oxidative stress and damage.
What are the effects of a G6P dehydrogenase deficiency?
Oxidative stress
→ oxidation of Hb by oxidant radicals and oxidised membrane proteins
What does Hb oxidation by oxidant radicals result in?
Denatured Hb aggregates and forms heinz bodies that bind to the membrane
What do oxidised membrane proteins do?
Reduced RBC deformability
What are patients with G6P dehydrogenase deficiency advised to do (and why)?
Avoid quinone based anti-malarial drugs and oxidative drugs because they can cause oxidative stress
What is pyruvate kinase deficiency?
- Autosomal recessive disorder
- Deficiency results in low intracellular ATP generation.
How does pyruvate kinase work in the glycolytic pathway?
- Generates energy in ATP
- To maintain red cell shape and deformability
- To regulate intracellular cation concentration via cation pumps (Na/K pump) 3 Na out and 2 K in.
What would pyruvate kinase deficiency result in?
low intracellular ATP generation thus affecting the ability to:
- To maintain red cell shape and deformability
- To regulate intracellular cation concentration
→
- More K leaves the cell hence it becomes hydrated and lyses easily
- Causes chronic non-spherocytic haemolytic anaemia
What are the global disorders?
- Thalassaemias – quantitative
- Variant haemoglobins – qualitative
What are the general issues in thalassaemias?
- Defect in the rate of synthesis of alpha or beta globin chain
- Reduced of absence of global chain
Why is it an issue if there’s a defect in the alpha or beta globin chain production?
Excess unpaired globin chains are unstable → heterogenous genetic disorders → ineffective erythropoeisis
What are the types of thalassaemia?
- Hydrop foetalis
- Beta thalassemia major
- Beta Thalassaemia intermedia
- Beta Thalassaemia minor
- Alpha thalassaemias
- Alpha Thalassaemia minor
What are the clinical features of beta thalassaemia major?
- Severe anaemia
- Progressive hepatosplenomegaly
- Facial bone abnormalities
- Mild jaundice
- Intermittent infections
What is hepatosplenomegaly?
Enlargement of liver and spleen
What can be seen in the peripheral blood of beta thalassaemia major?
- Microcytic hypochromic cells with decreased MCV, MCH, MCHC
- Anisopoikilocytosis (cells of different sizes and shapes)
- Target cells
- Nucleated RBCs
- Teardrop cells
- Reticulocytes >2%
What is thalassaemia intermedia?
Disorder with a clinical manifestation between thalassaemia major and minor
What are the signs of beta thalassaemia intermedia?
- Transfusion independent
- Diverse clinical phenotype
- Varying symptoms
- Increased bilirubin level
How do you diagnose thalassaemia intermedia?
Largely clinically
What are the symptoms of thalassaemia minor?
Asymptomatic
What is thalassaemia minor often confused with?
Iron deficiency
How do you diagnose thalassaemia minor?
Finding that HbA2 is increased in beta thalassaemia via Hb electrophoresis
What are the two types of alpha thalassaemias?
- HbH disease
and
- Hb barts hydrops syndrome
What causes Hb barts hydrops syndromes?
Deletion of all four globin genes
How long do patients with Hb barts hydrops syndrome live for?
They don’t - a chain is required for foetal and adult Hb.
What causes HbH disease?
3/4 alpha globin chains deleted
Where is HbH common?
South East Asia
What are the clinical features of HbH disease?
- Splenomegaly
- Hepatomegaly
What do you use to diagnose HbH disease?
Electrophoresis
What are the features of blood cells in HbH disease?
- Hypodromic microcytic
- Poikilocytosis
- Polychromasia
- Target cells
What are the features of alpha thalassaemia minor?
- Normal or mild HA
- MCV and MCH low
What does ‘sickle cell disease’ refer to?
All diseases as a result of inherited HbS
What is HbSS?
Sickle Cell Anaemia (Homozygous State)
What is HbAS
Sickle cell trait (heterozygous)
What is HbS caused by?
Single nucleotide substitution
Adenine → Thymine
What is Hb Sickling?
- As the blood travels through the body to deliver oxygen, there is repetitive exposure to alternative oxygenated and deoxygenated states that leads to membrane distortion of RBC and oxidative damage and Irreversible sickling of RBC.
- Deoxygenation of HbSS leads to intracellular Hb polymerization and loss of deformity of RBCs (so cannot go through smaller microcirculation) and would change the morphology of cells.
What are the clinical symptoms of sickle cell disease?
- Painful crises
- Aplastic crisis
- Frequent Infections
Why do sickle cell patients have frequent infections?
- Hyposplenism
- Splenic sequestration due to sickling and infarction in spleen
What are the clinical symptoms of acute sickling in sickle cell anaemia?
- Chest syndrome
- Splenic sequestration
- Stroke
What are the clinical symptoms of chronic sickling in sickle cell anaemia?
- Renal failure
- Avascular bone necrosis
What are the signs of Sickle cell in the lab?
- Anaemia (Hb 60-90)
- Reticulocytosis
- Increased NRBC
- Raised bilirubin
- Low creatine
How do you confirm a sickle cell diagnosis?
Solubility test:
- Expose blood to a reducing agent
- HbS precipitated
What is HbAS
Sickle cell trait (heterozygous)
