Haematology Session 2 Flashcards
What is the definition of anaemia?
A haemoglobin concentration lower than the normal range.
What does normal range of Hb vary with?
- age
- sex
- ethnicity
Why should the main cause of anaemia be established?
Anaemia is a sign of an underlying issue which should be treated to resolve the anaemia.
What are the symptoms of anaemia related to and what are they?
- Shortness of breath
- Palpitations
- Headaches
- Angina
- Weakness and lethargy
- Confusion
Related to insufficient delivery of oxygen.
What are the signs of anaemia?
- Tachycardia
- Pallor
- Systolic murmur
- Hypotension
- Tachypnoea
What are common signs associated with iron deficiency anaemia?
- Kolionychia - spoon nails
- Angular stomatitis - inflamed mouth corners
What are common signs associated with vit. B12 deficiency?
Glossitis - depapillation and inflammation of tongue
What are signs associated with thalassaemia?
Abnormal facial bone development - now rarely seen as it is preventable with early diagnosis.
Why might anaemia develop (bone marrow)?
- Reduced/dysfunctional erythropoiesis (marrow may not respond to the hormone)
- Abnormal haem synthesis
- Abnormal globin chain synthesis
(Bone marrow not producing RBCs)
Why might anaemia develop (peripheral RBCs)?
- Abnormal structure (degraded)
- Abnormal metabolism (G6PDH deficiency - broken down too fast)
- Mechanical damage
- EXCESSIVE BLEEDING
Why might anaemia develop because of the reticuloendothelial system?
Increased removal/hyperactivity.
Describe the normal process of erythropoiesis. *
- Low blood oxygen detected by kidney pericytes: stimulates prodution of erythropoietin
- EPO binds to receptors on erythroblasts which stimulates RBC production.
- Increased no. of RBCs means that oxygen levels rise
- Negative feedback on production of EPO.
What can anaemia result from when the process of erythropoiesis goes wrong?
- Lack of response (eg. kidney stops making EPO due to disease)
- Marrow cannot respond to EPO (chemo, parvovirus)
- No space for haemopoietic cells if marrow infiltrated - cancer or myelofibrosis
- Anaemia of chronic disease: iron not functionally available to marrow to make cells
- Myelodysplastic syndromes: abnormal marrow cells reduce RBC and WBC making capacity.
What mutations can occur in genes that encode globin chain proteins?
- Alpha thalassaemia
- Beta thalassaemia
- Sickle cell anaemia
What can defects in the haem synthesis pathway cause?
Sideroblastic anaemia (body is not able to use the iron it has to make haemoglobin).
Why can insufficient iron in diet lead to anaemia?
Not enough iron available to make haem
What does anaemia of chronic disease cause?
Functional iron deficiency (not available for erythropoiesis)
What is an inherited cause of haemolytic anaemia?
HEREDITARY SPHEROCYTOSIS
- Poor interactions between membrane and cytoskeleton
- Cells less flexible
- Damaged when squeezing through capillary
- Removed by RES
What is an acquired cause of haemolytic anaemia?
MECHANICAL DAMAGE
- Shear stress: cells passing through a defective heart valve
- Disseminated Intravascular Coagulation: small clots developing throughout blood stream, depletes clotting factors
- Heat damage (burns)
What is a sign of haemolytic anaemia from damage to cells?*
Presence of schistocytes (residues of RBCs)
Why might anaemia develop due to pyruvate kinase deficiency?*
- Defective glycolytic pathway means that cells get deficient in ATP = haemolysis
- No mitochondria so only anaerobic
- Membranes will look abnormal
Why might anaemia develop due to glucose-6-phosphate dehydrogenase deficiency?
- Will limit amount of NADPH, which regenerates glutathione to protect from oxidative stress
- Causes lipid peroxidation and protein damage
- Protein damage leads to formation of Heinz bodies
What are Heinz bodies and how do they cause anaemia??
- Aggregates of crosslinked haemoglobin
- Red cells get recognised as defective and are removed by RES, causing anaemia
When can anaemia develop from acute blood loss?
- Injury
- Childbirth
- Surgery
Why can anaemia develop from chronic NSAID use?
Those drugs induce GI bleeding by inhibiting cyclooxygenase (which synthesises prostaglandins) and have cytotoxic effects on the gut epithelium
What is the most common type of bleeding that causes anaemia?
Chronic bleeding - small amount of bleeding continued over a long period of time.
What are some examples of chronic bleeding?
- Heavy menstrual bleeding
- Repeated nosebleeds
- GI bleeding (blood in stool, eg. from ulcers)
- Haemorrhoids
Why might the function of the reticuloendothelial system cause anaemia?
Cells will be destroyed quicker as they are damaged/abnormal by the macrophages present in the spleen
Where can the cells become damaged?
- Intravascular haemolysis (in vessels)
- Extravascular haemolysis (in RES)
Why does splenomegaly occur in haemolytic anaemias?
The spleen has to work harder to remove the damaged cells.
What happens in autoimmune haemolytic anaemias?
- Antibodies bind to red cell membrane proteins
- Recognised by macrophages
- Destroyed by RES
What is myelofibrosis?
- Proliferating abnormal haematopoietic stem cells result in fibrosis.
- Too much fibrous tissue exists in the bone marrow, leaving very little space for haemopoiesis.
What do patients with myelofibrosis usually present with and why?
- Hepatosplenomegaly
Mutated progenitor cells from marrow colonise liver and spleen.
What is thalassaemia?
An inherited disorder resulting from decreased/absent alpha or beta globin chain production.
What causes thalassaemia?
An imbalance in composition of the alpha 2 beta 2 tetramer, meaning that the cells are smaller and paler (microcytic hypochromic).
What is haemoglobin H disease?
Lack of 3/4 alpha globin genes. Causes severe splenomegaly, microcytosis and haemolysis
How to work out the cause of anaemia?
- Size of RBC (macro, normo, or microcytic?)
- Presence/absence of reticulocytosis (does marrow want to make up for blood loss?)
What would an increase in reticulocyte number cause and why?
- Larger MCV as reticulocytes are larger cells
- Would also cause to reach the conclusion that the bone marrow is responding to blood loss correctly.
LOOK AT THE EVALUATION OF ANAEMIA SLIDE, SLIDE 13!
Ok :)
What are macrocytic anaemias?
Anaemias where the average red cell size is more than normal (higher MCV)
What are megaloblastic anaemias?
- Anaemias in which there is interference with DNA synthesis, so the nucleus develops much slower than the cytoplasm and cell division is delayed, leading to larger red cells as they grow waiting for nucleus to mature.
- Form megaloblasts: very large nuclei
What are the causes of megaloblastic anaemias?
- Vit. B12 / folate deficiency
- Drugs interfering with DNA synthesis
- Erythroid leukaemia
What are macronormoblastic anaemias?
Normal development, but the erythroblasts (precursors) are larger than normal and give rise to larger red cells.
What are the causes of macronormoblastic anaemias?
- Liver disease
- Alcohol toxicity
What is ‘stress’ erythropoiesis?
Conditions where there are high levels of erythropoietin and a high reticulocyte count, which leads to expanded erythropoiesis.
What causes stress erythropoiesis?
- Recovery from blood loss (anaemia/haemorrhage)
Where is folate absorbed?
Duodenum and jejunum (small intestine)
What is folate converted to by intestinal cells and what is it used for?
Tetrahydrofolate (FH4). Used to provide carbons for other reactions (eg. nucleotide synthesis)
Where is tetrahydrofolate stored?
Liver (3-4 months’ worth stored)
What are the causes of folate deficiency?
- Increased demands (eg. pregnancy)
- Poor diet intake
- Disease of jejunum/duodenum (eg. Coeliac)
- Urinary loss in heart and liver failure
- Drugs inhibiting dihydrofolate reductase - cause FUNCTIONAL DEFICIENCY
What are symptoms of folate deficiency?
- Hand/feet numbness and tingling
- Diarrhoea
- Muscle weakness
- Depression
- Reduced sense of taste
How much folic acid do pregnant women need and why?
- Prevents neural tube defects (spina bifida)
- 400 micrograms/day during first twelve weeks of pregnancy.
What is vitamin B12 needed for?
- DNA synthesis (essential cofactor due to role in folate metabolism)
- Needed for normal erythropoiesis
- Needed for normal function and development of CNS
How is B12 obtained and who needs supplements?
- Produced by bacteria, so mainly in animal origin foods
- Vegetarians and vegans need supplements
How is vitamin B12 absorbed? * (Slide 18)
- B12 binds to haptocorrin in the stomach that protects the vitamin from degradation by stomach acids.
- Haptocorrin B12 complex digested by PANCREATIC PROTEASES in small intestine
- B12 then binds to intrinsic factor
- B12-IF complex binds to cubam receptor and is taken up by receptor-mediated endocytosis
- B12 exits basolateral membrane through MDR1
- B12 binds to transcobalamin in blood and is transported
- Stored in the liver (3-6 year store)
What are the causes of B12 deficiency?
- Dietary (vegans)
- Pernicious anaemia
- Ileum disease
- Congenital lack of transcobalamin
- Chemical B12 inactivation
- Drugs that chelate (cannot absorb) intrinsic factor
What is pernicious anaemia?
Autoimmune disease that causes progressive exhaustion of B12 due to reduced or absent IF.
What are the 2 types of antibody found in pernicious anaemia?
Blocking - blocks binding of B12 to IF
Binding - prevents receptor-mediated endocytosis
What are the symptoms of B12 deficiency?
- Same as anaemia
- Paraesthesia
- Irritability
- Glossitis and ulcers
How can B12/folate deficiency affect the nervous system?
- Folate: neural tube defects in pregnancy
- Vitamin B12: focal demyelination
What can B12 deficiency result in?
- Reversible peripheral neuropathy
- Can cause irreversible system damage
What is the irreversible neurological condition caused by B12 deficiency and what is it?
- Subacute combined degeneration of the cord
- Posterior/lateral spinal cord column degeneration
What are the symptoms of subacute combined degeneration of the cord?
- Changes in mental state
- Gradual onset weakness, numbness and tingling that worsens progressively
What is the link between Vit. B12 and folate?* (SLIDE 21 KEY TO UNDERSTAND)
- Lack of Vit B12 will trap folate in its stable methytetrahydrofolate form and preventing its use in other reactions (eg. thymidine - replaced with uracil and leads to abnormal DNA)
- Methylene-tetrahydrofolate needed to create thymidine for DNA synthesis
- The methionine cycle in B12 is needed to produce methylated products that can produce adrenaline, melatonin, etc.
Why do B12 and folate deficiencies cause megaloblastic anaemias?
- Both lead to thymidine deficiency
- Uracil incorporated into DNA instead
- Error detected and constantly repaired by excision
= Asynchronous nuclear/cytoplasmic maturation
What happens to the nucleus of cells in B12/folate deficiency?*
- Nuclear maturation and cell divisions lag
- Large red cell precursors, open chromatin and very big nuclei
- Develop into very large red cells
What are some megaloblastic features that can be seen in a blood film?*
- Anisopoikilocytosis
- Tear drop red cells
- Ovalocytes
- Hypersegmented neutrophils (more lobes due to increased cell division numbers)
- Macrocytic red cells
What else can patients with megaloblastic anaemia develop?
Pancytopenia - decreased platelets/neutrophil counts
What are some investigations that need to be done to detect megaloblastic anaemia?* (SLIDE 24 KEY TO UNDERSTAND)
- Haemoglobin (low)
- MCV (usually raised)
- Plasma LDH (raised)
- Blood film
- Bone marrow
- Bilirubin
- B12/folaye
- Plasma methylmalonic acid (MMA) if test for B12 not reliable
- Check for IF antibodies if no evidence of other cause
How to treat folate deficiency?
Oral folic acid (start by taking 5mg/day then reduce to 1mg/day)
How to treat B12 deficiency in pernicious anaemia and why?
- Intramuscular hydroxycobalamine injections for life
- Cannot be oral as it won’t be absorbed due to reduced/absent IF and therefore must directly enter circulation
How to treat other causes of B12 deficiency?
Oral cyanocobalamine
How should patients with severe B12 deficiency have blood transfusions and why?
Very slowly with smaller volume as can result in high output cardiac failure
Why should hypokalaemia be considered a risk when treating severe pernicious anaemia?
Increased K+ requirement due to increased erythropoiesis will bring the numbers down.
What are some expected improvements after treatment?* KEY INFO SLIDE 25
Resolution of anaemia after 2 months and resolution of neuropathy after 3-6 months.
What are some features of microcytic anaemias?
- Reduced haemoglobin synthesis rate
- Microcytic RBCs
- Hypochromic cells
What are causes of reduced haem synthesis that lead to microcytic anaemia?
- Iron deficiency (not enough to synthesise)
- Lead poisoning (inhibits enzymes)
- Sideroblastic anaemia (inherited defect)
- Anaemia of chronic disease (functional deficiency)
What are the causes of reduced globin chain synthesis that can lead to microcytic anaemia?
- Alpha thalassaemia (deletion of 1+ alpha globin genes)
- Beta thalassaemia (mutation in beta-globin genes leading to reduction or absence of beta-globin
What does TAILS stand for?
Thalassaemia Anaemia of chronic disease Iron deficiency Lead poisoning Sideroblastic anaemia
What is iron needed for?
- Oxygen carrying (haemoglobin and myoglobin)
- Cofactor in enzymes (cytochromes + P450, catalase)
Why is free iron bad?
- Very toxic to cells (can participate in the Fenton reaction and create free radicals)
- Body has no mechanism for excreting iron and it can only be regulated how much will be absorbed
What is ferrous iron?
- Reduced form
- Fe2+
- Constituent of most dietary iron
- CAN be absorbed by the body
- Oxidised at a high pH to ferric iron
What is ferric iron?
- Oxidised form
- Fe3+
- Reduced at low pH to ferrous iron
- Constituent of most dietary iron
- CANNOT be absorbed by the body
What are oxidation and reduction?
- Oxidation is loss of electrons
- Reduction is gain of electrons
What is the difference between haem and non-haem iron?
- Haem iron is associated with haemoglobin (and therefore mostly from animal products)
- Non-haem iron is ferrous and ferric iron
How much iron is needed per day and where is it absorbed?
- 10-15 mg/day
- Absorption in duodenum and upper jejunum
What are good sources of haem iron?
- Liver
- Kidney
- Salmon
- Chicken
What are good sources of non-haem iron?
- Fortified cereal
- Beans
- Oats
- Barley
- Rice
What is the method of dietary iron absorption?*
- Chyme is delivered to duodenum
- Haem group is readily absorbed, and haem oxygenase converts it to ferrous iron
- Fe2+ is transported into the enterocyte by DMT1 (divalent metal transporter - cotransport)
- Fe3+ is converted to Fe2+ via reductase, which requires vit. C as an electron donor
How is iron transported out of the cell?*
- Ferroportin transport iron out of the enterocyte
- Hephaestin oxidises ferrous iron into ferric iron
- Transferrin transports 2 ferric iron molecules around the body
What is hepcidin and what does it do?
- Produced by liver
- Inhibits ferroportin function
- Iron transport therefore inhibited
What factors have a negative influence on iron absorption? Why?
- Tannins (tea)
- Phytates (chapattis/pulses)
- Fibre
Bind non-haem iron in the intestine and reduce absorption.
What promotes iron absorption? Why?
- Vitamin C & Citrate
Prevents formation of insoluble iron compounds and helps reduce ferric to ferrous.
What is functional iron and where is it in the body?
Available iron that is associated with proteins and enzymes.
- Haemoglobin ( around 2000mg)
- Myoglobin (around 300mg)
- Enzymes
- Transported
What is ferritin?*
- Soluble form of stored iron
- Globular protein complex with hollow core
- Has pores that allow iron to enter and then be released
What is haemosiderin?*
- Insoluble form of stored iron
- Stains as a dark precipitate
- Aggregates of clumped ferritin, denatured protein and lipid
- Accumulates in liver/spleen macrophages
How is cellular iron taken up?*
- Fe3+ bound transferrin binds to transferrin receptor
- Enters via receptor-mediated endocytosis
- Fe3+ released from transferrin and reduced to Fe2+
- Fe2+ transported into cytosol by DMT1
- Fe2+ can be stored in ferritin, taken up by mitochondria (use in cytochrome enzymes)
- Receptor recycled back to surface
- Iron exported via ferroportin
Where does most of the iron come from?
Recycling damaged/senescent blood cells by splenic macrophages or Kupffer cells in liver
Why do broken down blood cells serve as an iron source?
- Macrophages catabolise haem that’s released
- Iron is transported into blood via transferrin or returned into storage pool as ferritin in the macrophage
What does the regulation of iron absorption depend on?
- Dietary factors
- Iron strores
- Erythropoiesis
Sensed by enterocytes.
What are the control mechanisms for iron absorption?
- Transporter regulation
- Receptor regulaiton
- Hepcidin and cytokines
- Crosstalk between epithelial cells and other cells
How is hepcidin a negative regulator of iron absorption?
- Liver somehow detects serum iron if too high
- Hepcidin is released and internalises ferroportin and degrades it too
- Decreased by high erythropoietic activity
- Blocks iron transport
What is anaemia of chronic disease?*
- Functional iron deficiency
- Cytokines (IL6) released by immune cells
- Increases production of hepcidin by the liver, which then inhibits ferroportin
- Decreases iron release from RES and decreases absorption
- Also inhibits erythropoietin by kidney and erythropoiesis by bone marrow
- Plasma iron is reduced = ANAEMIA
What happens when iron is lost?
- Epithelia are desquamed
- Menstrual bleeding
- Sweat
- Pregnancy
What can be the causes of iron deficiency?
- Insufficient intake and poor absorption
- Physiological reasons (pregnancy)
- Pathological reasons (bleeding)
What are some causes of iron deficiency?
- Insufficient/Malabsorption of iron in diet (eg. vegan)
- Bleeding (menstruation/gastric)
- Increased requirement (pregnancy)
- Anaemia of chronic disease
What are the highest risk groups for anaemia?
- Infants
- Children
- Women of child-bearing age
- Geriatric
What happens when you have iron deficiency anaemia?
Must take supplements
What are the physiological effects of iron deficiency anaemia?
- Tiredness
- Pallor
- Reduced exercise tolerance
- Cardiac: angina, heart failure
- Headaches
What are symptoms of iron deficiency?
- Pica
- Cold hands and feet
- Epithelial changes
What are some epithelial changes in iron deficiency?*
- Angular cheilitis
- Glossitis
- Koilonychia
What are FBC blood parameters in iron deficiency?
- Low MCV
- Low MCHC
- Elevated platelet count
- Normal WBC count
- Low serum ferritin, iron and TIBC
- Low reticulocyte haemoglobin content
What are some peripheral blood smears in iron deficiency anaemia?*
- RBCs microcytic and hypochromic
- Anisopoikilocytosis
- Pencil cells and target cells
How do you test for iron deficiency?
- Plasma ferritin (reduced = iron deficiency)
- Normal/increased ferritin doesn’t exclude iron deficiency (can also increase in cancer/infection/inflammation)
- CHr test for functional iron deficiency (also low when with thalassaemia and inflammation)
How is iron deficiency treated?
- Oral iron supplements (poor compliance)
- Dietary advice
- Intramuscular iron injection
- IV iron
- Blood transfusion (severe anaemia with cardiac compromise)
Why is an excess of iron dangerous?
- Can exceed binding capacity of transferrin
- Deposited in organs as HAEMOSIDERIN
- Promotes free radical formations and organ damage
What is the Fenton reaction?*
Creates OOH and OH radicals (hydroxyl and hydroperoxyl
- Can cause damage to proteins & DNA
- Cause lipid peroxidation
What is transfusion-associated haemosiderosis?
- Accumulation of iron due to repeated blood transfusion
- 400ml blood = 200mg iron
- Problem with thalassaemia and sickle cell
- Iron chelating agents can delay it but not stop (e.g. desferrioxamine)
What can accumulation of iron do to organs?
- Liver cirrhosis
- Diabetes mellitus
- Hypogonadism
- Cardiomyopathy
- Slate grey skin
What is hereditary haemochromatosis?
- Autosomal recessive on HFE
- Normally interacts with transferrin receptor and reduces affinity
- Mutated HFE can’t bind to transferrin = no negative influence
- Also negative influence of hepcidin
- Too much iron enters cells
Why is it bad if too much iron enters cells?
Iron accumulates in end organs and causes damage
How is hereditary haemochromatosis treated?
Venesection
What are the symptoms of HH?
- Liver cirrhosis
- Diabetes mellitus
- Hypogonadism
- Cardiomyopathy
- Arthropathy
- Increased skin pigmentation (bronzed skin)
