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Clinical pathology specialities: Haematology > Haematology: Haemolytic Anaemias > Flashcards

Haematology: Haemolytic Anaemias Flashcards

1
Q

What is haemolytic anaemia?

A
  • Anaemia due to shortened red blood cell survival
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2
Q

Briefly describe the red blood cell cycle

A
  • Mature red blood cells are produce in the bone marrow
  • They then travel from bone marrow into the circulation (lose their nucleus on the way out)
  • They stay in circulation for about 120 days
  • In circulation they acquire chnages which are recognised by macrophages in liver/spleen that cause them to degrade RBCs after 120 days
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3
Q

What proteins/enzymes are required in the production of red blood cells?

A
  • Iron
  • B12/folate
  • Globin chains
  • Protoporphyrins
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4
Q

What are the main components of a mature red blood cell?

A
  • Plasma membrane - biconcave disc
  • Haemoglobin
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5
Q

What are the 2 main metabolic pathways of a mature red blood cell?

A
  • Glycolytic pathway
  • Hexose-monophosphate shunt - parallel to glycolytic pathway (produces NADPH, pentoses and ribose-5 phosphate)
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6
Q

What is haemolysis?

A
  • The rupture or destruction of of red blood cells leading to decreased red cell survival
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7
Q

Describe the body’s response to haemolysis?

A
  • Bone marrow increases red blood cell production
  • This leads to increased levels of reticulocytes in the circulation - this is called reticulocytosis
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8
Q

What is compensated haemolysis?

A
  • Occurs when red blood cell production is able to compensate for decreased red blood cell lifespan due to haemolysis
  • Results in haemoglobin level remaining normal
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9
Q

What is incompletely compensated haemolysis?

A
  • Occurs when red blood cell production is unable to compensate for decreased red bllod cell lifespan due to haemolysis
  • Results in reduced haemoglobin level
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10
Q

Name some of the main symptoms of haemolytic anaemias

A
  • Jaundice - Yellowing of skin, whites of eyes and mucous membranes
  • Pallor/fatigue
  • Splenomegaly - enlargement of the spleen
  • Dark urine
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11
Q

Why do haemolytic anaemias cause jaundice?

A
  • Excessive red blood cell break down leads to excessive levels of bilirubin in circulation
  • This leads to yellowing of skin etc. seen in jaundice
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12
Q

They are 2 types of crises associated with haemolytic anaemia, Explain these 2 crises

A
  • Haemolytic crisis - Occurs when there’s an increased level of haemolysis due to an infection leading to increased anaemia and jaundice
  • Aplastic crisis - Occurs when person is infected with parvovirus which causes a rapid decrease in Hb levels leading to anaemia. Reticulocytopenia also occurs as parvovirus affects erythroblasts, and therefore eryhtropoiesis, in bone marrow.
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13
Q

Name some symptoms of chronic haemolytic anaemias

A
  • Pigment gallstones - due to breakdown of excess bilirubin
  • Splenomegaly
  • Leg ulcers - due to free Hb collects and removes nitric oxide
  • Folate deficiency - due to increased use
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14
Q

Describe the laboratory findings/results of tests for haemolytic anaemia

A
  • Normal/decreased haemoglobin
  • Increased reticulocyte count
  • Increased unconjugated bilirubin
  • Increased LDH (lactate dehydrogenase) - released wehn red cells are broken down
  • Low serum haptoglobin - protein that binds free haemoglobin
  • Increased urobilinogen
  • Increased urinary haemosiderin
  • Abnormal blood film
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15
Q

What are some of the cahracteristics of the blood film of someone with a haemolytic anaemia?

A
  • Presence of reticulocytes
  • Polychromasia - high levels of immature red blood cells
  • Presence of nucleated red blood cells
  • Poikilocytes - abnormally shaped red blood cells
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16
Q

What are the different ways that haemolytic anaemias can be classified?

A
  • Classification based on inheritance:
    • Inherited
    • Acquired
  • Classification based on site of RBC destruction:
    • Intravascular
    • Extravascular
  • Classification beased on origin of RBC damage:
    • Intrinsic
    • Extrinsic
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17
Q

Name some congenital/acquired disorders that lead to heamolytic anaemia

A
  • Membrane disorders:
    • Spherocytosis
    • Elliptocytosis
  • Enzyme disorders:
    • Glucose-6-phosphate dehydrogensae (G6PD) deficiency
    • Pyruvate Kinase deficiency
  • Haemoglobin disorders:
    • Sickle Cell Anaemia
    • Thalassaemias
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18
Q

Name some acquired causes of haemolytic anaemias

A
  • Autoimmune causes
  • Drugs
  • Mechanical - leaky heart valves
  • Microangiopathic - severe hypertension
  • Infections - malaria
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19
Q
A
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20
Q

Describe process of intravascular haemolysis

A
  • Red blood cell broken down in circulation causing it to release its haemoglobin, iron and bilirubin
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21
Q

What conditions does intravascular haemolysis lead to?

A
  • Haemoglobinaemia - Excess free haemoglobin in blood
  • Methaemalbuminaemia - Breakdown of haemoglobin forms haem and methaem which binds to albumin to form methemalbumin
  • Haemoglobinuria - Excess haemoglobin in urine
  • Haemosiderinuria - Haemosiderin in urine
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22
Q

There are two main types of red cell membrane disorder that can cause haemolytic anaemias. Name these 2 types of red cell membrane disorder and give examples of proteins that can be affected by them.

A
  • Defects in proteins involved vertical interaction:
    • Spectrin
    • Band 3
    • Protein 4.2
    • Ankyrin
  • Defects in proteins involved in horizontal interaction:
    • Protein 4.1
    • Glycophorin C
    • Spectrin – Can cause hereditary pyropoikilocytosis (HPP)
23
Q

What condition is usually caused by disorders affecting vertical interaction?

A
  • Hereditary spherocytosis
24
Q

What condition is usually caused by disorders affecting horizontal interaction?

A
  • Hereditary elliptocytosis
25
Q

What are some of the main characteristics of hereditary spherocytosis?

A
  • Most common hereditary haemolytic anemia
  • Shows autosomal dominant inheritance
  • Bone marrow makes biconcaves RBCs but they lose membrane as they go around circulation causing them to become spherical
26
Q

What are some of the clinical feautures of hereditary spherocytosis?

A
  • Can be asymptomatic to severe haemolysis - shows no symptoms of haemolysis
  • Neonatal jaundice - Bilirubin in babies can cross blood-brain barrier and cause brain damage
  • Jaundice
  • Splenomegaly
  • Pigment gallstones
  • Reduced eosin-5-maleimide (EMA) binding – binds to band 3, a membrane protein.
27
Q

How can you manage/treat hereditary spherocytosis?

A
  • Monitor condition
  • Folic acid supplemements
  • Blood transfusion
  • Splenectomy - removal of spleen
28
Q

Glucose-6-phosphate dehydrogenase is involved in the hexose monophpsphate pthway/shunt. What is the function of this pathway?

A
  • Produces NADPH as well as reduced glutathione (GSH)
  • Reduced glutathione is an anti-oxidant and so one of the functions of the pathway is to protect cell from effects of oxidative stress
29
Q

Glucose-6-phosphate dehydrogenase deficiency means cells are less able to protect against effects of oxidative stress. What are some of the effects of oxidative stress on a red blood cell?

A
  • If oxidant radicals come into contact with RBCs they will cause oxidation of Haemoglobin
  • This causes haemoglobin to denature and aggregate
  • This forms Heinz bodies which bind to the RBC membrane
  • This causes membrane proteins to also become oxidised – leads to reduced RBC deformability
30
Q

What are some characterisitics of glucose-6-phosphate deficiency?

A
  • Hereditary, X-linked disorder
  • Common in African, Asian, Mediterranean and Middle Eastern populations
  • Two types: Type A (mild) and Type B (severe)
  • Clinical features range from asymptomatic to acute episodes to chronic haemolysis (rare)
31
Q

Name some things that can cause oxidation leading to oxidative haemolysis in patients with glucose-6-phosphate deficiency

A
  • Infections
  • Fava/ broad beans
  • Drugs - e.g. Dapsone, Nitrofurantoin and Ciprofloxacin
32
Q

What characetristics would a blood film of somebody with glucose-6-phosphate deficiency have?

A
  • Bite cells
  • Blister cells & ghost cells
  • Heinz bodies - RBCs with oxidised haemoglobin (identified using methylene blue stain)
33
Q

What is the function of pyruvate kinase?

A
  • Catalyses transfer of phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP) to form pyruvate and ATP.
34
Q

What are some characteristics of pyruvate kinase deficiency?

A
  • Autosomal recessive
  • Causes chronic haemolytic anaemia
  • Condition can be improved via splenectomy
35
Q

What characteristics would a blood film of somebody with pyruvate kinase deficiency have?

A
  • Ecchinocytes
  • May also see polychromasia
36
Q

Briefly describe structure of haemoglobin

A
  • Ferrous iron (Fe2+) and Protoporphyrin IX (which binds iron) form haem complex
  • Also contains Globin proteins
37
Q

What are the 3 types of haemoglobin?

A
  • HbA - α2β2
  • HbA2 - α2δ2 (makes up 2-3.5% of adult Hb)
  • HbF - α2γ2
38
Q

What are the different types of Haemoglobinopathies (inherited genetic conditions affecting the haemoglobin)?

A
  • Thalassaemias - Increased/ decreased production of a globin chain (structurally normal)
  • Variant haemoglobins - Production of a structurally abnormal globin chain e.g. sickle cell anaemia
39
Q

What is Thalassaemia and what problems does it cause?

A
  • Disorder in which there’s imbalanced alpha and beta chain production
  • Excess unpaired globin chains are unstable which causes a number of problems:
    • They precipitate and damage RBC and their precursors
    • They lead to Ineffective erythropoiesis in bone marrow
    • They cause Haemolytic anaemia
40
Q

What is Beta thalassaemia?

A
  • Form of thalassaemia caused by caused by reduced or absent synthesis of the betachains of hemoglobin
  • Autsomal recessive disorder so a person can have the beta thalassaemia trait or can have the disease (beta thalassaemia major).
41
Q

What are some characteristics of the beta thalassaemia trait?

A
  • Asymptomatic
  • Causes microcytic hypochromic anaemia
  • Low Hb, MCV, MCH
  • Increased RBC
  • HbA2 increased
42
Q

Children with beta thalassaemia are transfusion dependent within 1st year of life. What problems occur if they don’t have a blood transfusion?

A
  • Failure to thrive
  • Progressive hepatosplenomegaly - swelling of liver and spleen
  • Bone marrow expansion – skeletal abnormalities
  • Death in 1st 5 years of life from anaemia
43
Q

What are some of the side effects of a blood transfusion for children with beta thalassaemia?

A
  • Iron overload - this can lead to:
    • Endocrinopathies
    • Heart failure
    • Liver cirrhosis
44
Q

What is the mutation that causes sickle cell disease and how does it lead to sickle cell diease?

A
  • Point mutation in beta globin gene that causes glutamate to be converted into valine at position 7
  • This causes production of insoluble haemoglobin which polymerises when deoxygenated
  • This leads to sickle shaped RBCs
45
Q

What are some of the acute complications associated with sickle cell disease?

A
  • Stroke: ischaemic & haemorrhagic
  • Splenic sequestration - sickled red blood cells become trapped in the spleen acusing it to enlarge
  • Aplastic crisis
  • Chest syndrome
  • Leg ulcers
46
Q

What are some of the chronic complications associated with sickle cell disease?

A
  • Chronic lung disease (bronchiectasis)
  • Chronic renal failure
  • Pulmonary hypertension
  • Delayed puberty
47
Q

What are some clinical feautures of sickle cell disease?

A
  • Painful crises
  • Aplastic crises
  • Infections
48
Q

What laboratory results would you expect someone with sickle cell disease to have?

A
  • Anaemia (Hb often 65-85)
  • Reticulocytosis
  • Increased no. of nucleated red blood cells (NRBC)
  • Raised bilirubin
  • Low creatinine
49
Q

What diagnostic tests can be used to confirm diagnosis of sickle cell anaemia?

A
  • Solubility test - Expose blood to reducing agent and if haemoglobin precipitates then person has HbS
  • Electrophoresis
50
Q

What are the 2 types of acquired haemolytic anaemia?

A
  • Anaemia due to immune haemolysis
  • Anaemia due to non-immune haemolysis
51
Q

What are the 2 types of immune haemolysis?

A
  • Autoimmune
  • Alloimmune
52
Q

What are some causes of autoimmune haemolysis?

A
  • Idiopathic
  • Drug-mediated
  • Cancer associated - e.g. some lymphoproliferative disorders such as chronic lymphocytic anaemia
53
Q

What are some causes of alloimmune haemolysis?

A
  • Transplacental transfer - Haemolytic disease of the newborn:
  • Transfusion related - Acute or delayed haemolytic transfusion reaction
54
Q

What are some causes of non-immune acquired haemolysis?

A
  • Paroxysmal nocturnal haemoglobinuria
  • Fragmentation haemolysis - Can be mechanical or microangiopathic
  • Severe burns
  • Some infections - e.g. malaria

Clinical pathology specialities: Haematology (8 decks)

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