Haematology Flashcards
What is the definition of anaemia
Anaemia is defined as a low level of haemoglobin in the blood
What are the sub groups of anaemia
Anaemia is initially subdivided into three main categories based on the size of the red blood cell (the MCV). These have different underlying causes:
- Microcytic anaemia(low MCV indicating small RBCs)
- Normocytic anaemia(normal MCV indicating normal sized RBCs)
- Macrocytic anaemia(large MCV indicating large RBCs)
What are the variables for anaemia parameters
- Red blood cell (RBC) count
- Haemoglobin (Hb) concentration
- Haematocrit
- MCV (mean cell volume - a measurement of the size of RBCs)
What are the types of anaemia
Microcytic
Normocytic (Haemolysis - increase in reticulocytes and Bone marrow failure - decrease in reticulocytes)
Macrocytic (Megaloblastic and nonmegaloblastic)
What are the mean cell volume of microcytic anaemia
<80fL
What are the causes of microcytic anaemia
- T–Thalassaemia
- A–Anaemia of chronic disease
- I–Iron deficiency anaemia
- L–Lead poisoning
- S–Sideroblastic anaemia
What are iron deficiency anaemia risk factors
- Generally occurs in people with chronic slow bleeding - where the iron in the red blood cells is lost with the blood e.g. women with frequent or heavy menstruation or patients with colon cancer.
- Pregnancy: due to increased iron requirements for fetal development.
- Lack of iron in the diet.
- Can be due to refractory iron deficiency due to H.pylori infection: the bacteria can sequester iron and it can cause gastric bleeding, or inflammatory bowel disease or coeliac disease, both of which can cause malabsorption.
What is the treatment plan for iron deficiency anaemia
- Treat the cause
- Oral iron supplements
- If oral iron isn’t effective, or the side effects can’t be tolerated, IV iron can be used instead.
What is anaemia of chronic disease and when does it develop
- Characterised by inflammation. During inflammation the body likes to store away iron.
- Often develops in people with chronic inflammatory diseases, like infections, autoimmune disorders, and various cancers, and typically resolves once that underlying condition resolves.
What is thalassaemia
- Issue with the production of globin chains in Hb
- Alpha thalassaemia: issue with the alpha chain
- Beta thalassaemia: issue with the beta chain
- Can cause disease of varying severity depending on number of mutations
What is the treatment for thalassaemia
- Mild thalassaemia’s don’t require treatment
- Severe thalassaemia’s require blood transfusions + iron chelating agents to prevent iron overload
What is sideroblastic anaemia characterised by
- Characterised by sideroblasts: immature red blood cells found in the bone marrow.
- These erythrocytes cannot utilise iron for the synthesis of heme, so iron accumulates inside the mitochondria.
What are the causes of sideroblastic anaemia
- Congenital e.g. genetic mutations
- Acquired e.g. myelodysplastic syndrome, excessive alcohol use, copper or vitamin B6 deficiency, or intake of certain antimicrobial drugs.
What is the treatment for sideroblastic anaemia
- Treatment depends on the cause e.g.
- Stopping the use of alcohol or medication
- Some congenital cases respond to vitamin and mineral supplements
- Myelodysplastic syndrome requires a bone marrow transplant.
What is the mean cell volume for normocytic anaemia
80-95fL
What are the causes of normocytic anaemia
Generally caused by the destruction of RBCs. Sometimes replacement of RBC is not possible, due to bone marrow suppression or chronic kidney disease
Causes: (3 As and 2 Hs)
- A–Acute blood loss
- A–Anaemia of Chronic Disease
- A–Aplastic Anaemia e.g. bone marrow suppression or chronic kidney disease (lack of EPO)
- H–Haemolytic Anaemia
- H–Hypothyroidism
What are examples of inherited haemolytic anaemia
- Hereditary spherocytosis
- Glucose 6 phosphate dehydrogenase (G6PD) deficiency
- Sickle cell disease
- Thalassaemia
Describe hereditary spherocytosis
- A genetic disorder caused by defects in the structural proteins ankyrin, spectrin, or band 3
- Without these proteins, the red blood cells can’t keep their shape and become spherical
- The misshapen cells are less flexible than normal red blood cells and get stuck in the spleen, where they are destroyed by macrophages
What is the treatment for hereditary spherocytosis
Splenectomy
What is Glucose 6 phosphate dehydrogenase (G6PD) deficiency
- An X-linked recessive disorder that results in defects of the enzyme
- Normally, it protects the red blood cells from oxidative stress, so in affected individuals, there’s haemolysis when there is exposure to oxidative stressors
- When there’s oxidative stress, haemoglobin gets damaged and forms heinz bodies inside the red blood cell.
- Macrophages in the spleen detect the abnormal red blood cells and try to remove the heinz bodies by taking out a chunk of the cell.
- During a haemolytic attack, the deficient cells die
What is the treatment for G6PD deficiency
- Acute phase treatment: blood transfusions
- Prevention of haemolytic attack: avoid the triggers; splenectomy
Describe sickle cell disease
- An autosomal recessive disorder
- Caused by a mutated haemoglobin gene that encodes for an abnormal adult hemoglobin called HbS
- When there’s acidosis, hypoxia, or dehydration, the red blood cells sickle, and that causes either haemolysis or capillary obstruction causing ischemia and pain.
- These episodes are known as sickle crises
What is the treatment for sickle cell disease
- IV fluids, oxygen, and pain control are used to manage the symptoms
- Blood transfusion may be needed + iron chelating agents to prevent iron overload
- Hydroxycarbamide: increase level of HbF, as this is protective
What are examples of acquired haemolytic anaemia
- Autoimmune haemolytic anaemia: red blood cells are attacked by either IgM or IgG antibodies
- IgM: cause cold agglutinin - haemolysis happens in the cool extremities, and it’s associated with infections like mycoplasma and mononucleosis.
- IgG: cause warm agglutinin - haemolysis happens when it’s warm, and it’s associated with lupus and drugs like penicillin and cephalosporin.
- Non-immune (e.g. mechanical trauma, hypersplenism, infections, drugs)
What are the mean cell volume for macrocytic anaemia
> 95fL
What are macrocytic anaemias caused by
Caused by problems in producing RBCs
Megaloblastic causes:
- A result of impaired DNA synthesis preventing the cell from dividing normally, caused by
- B12 deficiency
- Folate deficiency
Non-megaloblastic causes:
- Alcohol
- Reticulocytosis(usually from haemolytic anaemia or blood loss)
- Hypothyroidism
- Liver disease
- Drugs such asazathioprine
Why is B12 deficiency problematic and what causes it
- Found in animal protein so vegans who don’t take supplements may be deficient
- May also be an issue with malabsorption
- Normally, meat or dairy are broken down in the stomach and the B12 is released. Intrinsic factor, made by parietal cells binds to the B12. Then, the B12-intrinsic factor complex moves through the intestines to the terminal ileum, where the complex is absorbed
- In pernicious anaemia: IgA antibodies attack intrinsic factor or the parietal cells
- In Crohn’s disease: the terminal ileum is damaged which affects absorption
- In patient’s with a gastric bypass, food moves through too quickly for effective absorption of B12
- B12 is used throughout the body, so people with B12 deficiency develop a variety of neurologic symptoms.
What is the treatment for B12 deficiency
- Oral B12 supplements
- If issues with malabsorption, extremely high doses or IV B12 could be given
What may cause folate deficiency
- We have up to six weeks supply of folate in the body, but this can get used up even quicker during pregnancy.
- Individuals on a restricted diet may also have folate deficiency
What is the treatment for folate deficiency
Folate supplements
What are the general clinical manifestations of anaemia
- Generic signs:
- Pale skin
- Conjunctival pallor
- Tachycardia
- Bounding pulse
- Raised respiratory rate
- Postural hypotension
- Shock
- Symptoms
- Tiredness
- Shortness of breath
- Headaches
- Dizziness
- Palpitations
- Confusion
- Syncope
- Worsening of other conditions such as angina, heart failure or peripheral vascular disease
- Pica (abnormal cravings) and hair loss may signify iron deficiency anaemia
What are specific clinical manifestations of anaemias and what do they indicate
- Koilonychia: spoon shaped nails and can indicate iron deficiency
- Angular chelitis (red, swollen patches in the corners of your mouth)can indicate iron deficiency
- Atrophic glossitis: smooth tongue due to atrophy of the papillae and can indicate iron deficiency
- Brittle hair and nails: can indicate iron deficiency
- Jaundice:occurs inhaemolytic anaemia
- Bone deformities: occur inthalassaemia
- Oedema, hypertension and excoriations on the skin:can indicatechronic kidney disease
What are the primary investigations for anaemia
- Full blood count forhaemoglobinandMCV
- Blood film
- Reticulocyte count
- Ferritin (an iron store)
- B12 and folate
- Bilirubin (raised in haemolysis)
- Direct Coombs test (autoimmune haemolytic anaemia)
- Haemoglobin electrophoresis (haemoglobinopathies)
What are further investigations for anaemia
- Oesophago-gastroduodenoscopy(OGD) andcolonoscopy:to investigate for a gastrointestinal cause of unexplainediron deficiency anaemia. This is done on an urgent cancer referral for suspected gastrointestinal cancer.
- Bone marrow biopsy:may be required if the cause is unclear
What is the direct Coombs test for
To detect antibodies that are stuck to the surface of RBCs
What is the management plan for anaemia
Management depends on establishing the underlying cause and directing treatment accordingly. Iron deficiency can be treated with iron supplementation. Severe anaemia may require blood transfusions.
Describe the make up of haemoglobin
- Haemoglobin is made of four haem molecules which contain iron. This iron molecule is what binds to oxygen, so each haemoglobin molecule can bind four molecules of oxygen.
- In addition, iron is also an important part of proteins like myoglobin, which delivers and stores oxygen in muscles; and mitochondrial enzymes like cytochrome oxidase, which help generate ATP.
What is the total iron content and distribution among different structures
- Each day, around 1-2 mg of iron is absorbed and 1-2 mg is lost from the body. The total iron content withinour body is approximately 3-4 grams, whichis distributed among different structures:
- Hb:2-3 grams
- Plasma iron (e.g. bound to transferrin):3-7 mg
- Iron-containing proteins (e.g. myoglobin):300-400 mg
- Stored iron (e.g. ferritin, haemosiderin):1 gram
Describe the absorption of iron in the GI tract
Absorption of iron from enterocytes in the gastrointestinal tractis highly regulatedto match the loss of iron from the body each day. When the rate of iron absorption cannot keep up with the rate of iron loss, it will lead to depletion of iron stores within the body and eventually IDA.
Describe how we get iron from our diets
- Our diet contains two forms of iron.
- The first is heme iron, or iron bound to haemoglobin or myoglobin. This is in the ferrous, or Fe2+, state.
- The other form is non-heme iron, which is free iron molecules in the ferric, or Fe3+, state.
- When food is broken down in the stomach, iron is released.
- Heme iron is absorbed directly into the duodenal cells, where it is broken down to release Fe2+ molecules.
- Non-heme iron, however, needs to be reduced to heme iron first. The stomach’s hydrochloric acid activates a group of enzymes in the duodenal cells, collectively called ferri-reductase.
- Fe2+ molecules then bind to a protein in the duodenal cells called ferritin, which temporarily stores the iron.
- When iron is needed in the body, some Fe2+ molecules are released from ferritin and transported into the blood, where the enzyme hephaestin converts them back to the Fe3+ state.
- Fe3+ molecules then bind to an iron transport protein called transferrin that carries iron to various target tissues and releases them there.
- Fe3+ enters these various tissue cells, where there’s some more ferritin that can store them for future use.
Define iron deficiency anaemia
Anaemia (low levels of Hb in the blood) caused by iron deficiency
What is the epidemiology of iron deficiency anaemia
Most common cause of anaemia worldwide
What are the risk factors for iron deficiency anaemia
- Vegetarian/ vegan diet
- H.pylori infection
- Pregnancy
- Young children and adolescents
- Inflammatory bowel disease
- Coeliac disease
- Certain drugs e.g. PPIs
What are the examples of where iron stores can be used up causing the patient to become iron deficient
- Dietary insufficiency
- Loss of iron e.g. inheavy menstruation, gastric ulcers, and colon cancer
- Inadequate iron absorption e.g. after gastric surgery resulting in less HCl production, Crohn’s disease, coeliac disease
- Increased requirements e.g. during pregnancy, growing children and adolescents
Other causes include H.pylori infection, which causes gastric ulcers and gastrointestinal bleeding. H.pylori also traps dietary iron for itself, preventing it from reaching the duodenum.
Describe the absorption of iron
Iron is mainly absorbed in the duodenum and jejunum. It requires the acid from the stomach to keep the iron in the soluble ferrous (Fe2+) form. When there is less acid in the stomach, it changes to the insoluble ferric (Fe3+) form. Therefore, medications that reduce the stomach acid, such as proton pump inhibitors (lansoprazole and omeprazole) can interfere with iron absorption.
Describe the pathophysiology of iron deficiency anaemia
Regardless of the cause, iron deficiency leads to impaired haemoglobin production.
Since there’s not enough haemoglobin for a normal sized RBC, the bone marrow starts pumping out microcytic RBCs. These cells containing less haemoglobin are called hypochromic, since they appear pale.
These microcytic RBCs can’t carry enough oxygen to the tissues - hypoxia.
Hypoxia signals the bone marrow to increase RBC production.
The bone marrow goes into overdrive and pumps out incompletely formed RBCs.
In addition to anaemia, iron deficiency also results in defective production of mitochondrial enzymes that generate necessary ATP for growth and development and this affects fast growing tissues, like hair and nails the most.
Sometimes iron deficiency anaemia may occur in the context of Plummer-Vinson syndrome, resulting in features such as glossitis and oesophageal webs.
What are the clinical manifestations of iron deficiency anaemia
- Signs
- Pallor
- Conjunctival pallor
- Glossitis
- Koilonychia (spoon-shaped nails)
- Angular stomatitis
- Symptoms
- Fatigue
- Dyspnoea
- Dizziness
- Headache
- Nausea
- Bowel disturbance
- Hairloss
- Pica (abnormal cravings)
- Possible exacerbation of cardiovascular co-morbidities causing angina, palpitations, and intermittent claudication.
Describe the primary investigations for iron deficiency anaemia
- FBC: low Hb, low MCV, low MCHC
- Iron studies:
- Serum iron
- Serum ferritin: low in anaemia
- Total iron binding capacity: can be used as a marker for how much transferrin is in the blood. Increased in anaemia
- Transferrin saturation: gives a good indication of the total iron in the body. Decreased in anaemia
What is the normal range for the following; serum ferritin, serum iron, total iron binding capacity
Serum ferritin - 12-200ug/L
Serum iron - 14-31 micromol/L
Total iron binding capacity - 54-75 micromol/L
What are other investigations for iron deficiency anaemia
- Oesophago-gastroduodenoscopy (OGD) and a colonoscopy to look for cancer of the gastrointestinal tract: for new iron deficiency in an adult without a clear underlying cause
- Bone marrow biopsy:may be required if the cause is unclear
What is the management for iron deficiency anaemia
- Treat the underlying cause
- Oral iron supplements: ferrous sulphate or ferrous fumarate
- Side effects: constipation and black coloured stools, diarrhoea, nausea and dyspepsia/epigastric discomfort.
- Iron infusion e.g. cosmofer
- Blood transfusions may be needed in severe cases
Define anaemia of chronic disease
Anaemia of chronic disease (ACD) is a complex and multi-factorial condition due to a chronic inflammatory process from underlying infection, malignancy or systemic disease.
ACD is classically described as a normocytic, normochromic anaemia, but can also be microcytic anaemia.
Describe the epidemiology of anaemia of chronic disease
ACD is the second most common cause of anaemia worldwide, and commonly seen among hospitalised patients.
Describe the pathophysiology of anaemia of chronic disease
- ACD may be associated with many chronic disease states like infections, malignancy, diabetes, or autoimmune disorders.
- The continuous inflammation generated by chronic disease impairs iron metabolism and, in turn, RBC production.
- In general, the disease mechanism is a two fold process; decreased RBC lifespan and decreased RBC production.
- Shortened RBC lifespan is a result of direct cellular destruction via toxins from cancer cells, viruses, or bacterial infections.
- Decreased RBC production involves several mechanisms:
- In chronic disease states, cytokines mediate this pathologic process in the kidney, immune system, and the GI tract. Two cytokines called TNF-a and IFN-y inhibit the production of erythropoietin in the kidney, which subsequently prevents RBC production in the bone marrow.
Additionally,
- TNF-a promotes RBC degradation in macrophages via phagocytosis
- IF-Y increases the expression of a protein channel called divalent metal transporter one on the surface of macrophages. This channel serves as a pathway for iron to enter the macrophage at increased rates, so less iron is available for the production of haemoglobin.
- IL-10 mediates the expression of increased ferritin receptors on the surface of macrophages, which then sequesters even more iron.
- IL-6 also works in the liver by increasing production of a molecule called hepcidin, which blocks further uptake of iron from the small intestine.
What are the clinical manifestations of anaemia of chronic disease
- Fatigue
- Pallor
- Shortness of breath
- Headache
- Dizziness
- May worsen palpitations, angina and intermittent claudication
What are the primary investigations for anaemia of chronic disease
- FBC: normocytic normochromic anaemia (approx. 75%) OR microcytic anaemia
- CRP
- Blood film
- Haematinics: check for iron, B12 and folate deficiencies
- Iron studies:
- Serum ferritin: normal or raised
- Serum iron: tends to be low
- Total iron binding capacity: tends to be low
What are further investigations for anaemia of chronic disease
Marrow biopsy: iron stores are normal or increased
What is the management for anaemia of chronic disease
- Treatment of underlying cause e.g.
- Antibiotics for infection
- Surgical resection of tumour
- Treatment of diabetes
- EPO injections
- Parenteral iron
- Transfusions
Define hereditary spherocytosis
Hereditary spherocytosis (HS) is an inherited haemolytic anaemia and is autosomal dominant in the majority of cases (75%), but can also be autosomal recessive.
Describe the epidemiology of HS
- HS is the most common genetic haemolytic disease.
- It is more common in Northern Europe and North America but can affect people of any race.
- It is diagnosed in 1 in 2000 people, whilst a large proportion of these individuals are asymptomatic
What are the risk factors of HS
- Family history
- Northern European descent
Describe the pathophysiology of HS
- HS occurs due to a defect in red cell membrane proteins, such as ankyrin and spectrin.
- This causes red blood cells (RBCs) to lose their biconcave shape and appear spherical.
- Subsequently, there is accelerated degradation of RBCs in the spleen (extravascular haemolysis), resulting in a normocytic anaemia.
- Splenomegaly occurs because the spleen has to work harder (hypersplenism) to clear out the abnormal RBCs and their products.
- As haemolysis occurs, haemoglobin is broken down to bilirubin by macrophages, which increases the risk of gallstones and cholecystitis.
- Patients can have episodes of haemolytic crisis, often triggered by infections, where the haemolysis, anaemia and jaundice is more significant.
- Patients with hereditary spherocytosis can develop aplastic crisis. During aplastic crisis there is increased anaemia, haemolysis and jaundice, without the normal response from the bone marrow of creating new red blood cells. This is often triggered by infection with parvovirus.
What are the clinical manifestations of HS
- Signs
- Splenomegaly
- Pallor
- Jaundice
- Tachycardia
- Flow murmur
- Symptoms
- Fatigue
- Dizziness
- Palpitations
- RUQ pain: due to gallstones
- Neonatal jaundice: in 50% of patients
- Failure to thrive
What is the diagnostic criteria for HS
No further tests are needed for diagnosis, if:
- Family history of HSand
- Typical clinical featuresand
- Positive laboratory investigations (spherocytes, raised MCHC, increase in reticulocytes)
What are the first line investigations for HS
- FBC:normocytic anaemia with an increased reticulocyte count and raised MCHC
- MCHC is increased as spherical RBCs lead to water diffusing out of the cell
- Blood film:spherocytosis
- LFTs:increased (unconjugated) bilirubin due to haemolysis
- Coombs test:negativein hereditary spherocytosis. This is an important test to perform as spherocytes are also seen in autoimmune hemolytic anaemia (Coombs positive) and will, therefore, allow for differentiation between the two conditions
What is the management for HS
- Phototherapy or exchange transfusion:conducted in neonatal jaundice to reduce bilirubin levels
- Blood transfusion:patients should be managed with transfusions for symptomatic anaemia until splenectomy is possible or deemed appropriate
- Folic acid: all patients require daily folic acid supplementation until splenectomy
- Splenectomy:removing the spleen reduces haemolysis
- Splenectomy is delayed until patients are> 6 years oldto reduce the risk of post-splenectomy sepsis
- Patients must bevaccinatedagainst encapsulated bacteria and be prescribed lifelongphenoxymethylpenicillin
What are the complications for HS patients
- Gallstones: the high level of bilirubin due to haemolysis increases the risk of gallstones
- Aplastic crisis: parvovirus B12 infection attacks erythroid precursors in the marrow, resulting in anaemia with reduced reticulocyte count. Any patient with a haemolytic condition is at risk due to reduced RBC life span
- Bone marrow expansion:in conditions where there is a chronic, increased need for RBC production, such as haemolytic anaemias, bone marrow can expand. This particularly affects the face and skull
- Post-splenectomy sepsis:prevented by lifelong penicillin and vaccination againstS. pneumoniae,H. influenzae, influenza, and meningitis A&C. Vaccination is offered two weeks prior to the procedure
What is the prognosis for HS patients
Most patients with HS are asymptomatic with a near-normal Hb post-splenectomy, as this increases RBC lifespan
What is the function of G6PD
- Normally, as a part of the metabolic process, our body produces free radicals like hydrogen peroxide, or H2O2.
- Free radicals can damage the cells in many ways including destroying the DNA, proteins, and the cell membrane.
- Glutathione acts as an antioxidant and goes around and neutralises these free radicals.
- In order to function, glutathione needs to be in the reduced state where they can donate an electron to the H2O2 and convert them into harmless water and oxygen.
- However this causes the glutathione to become oxidised, so before it can be reused, glutathione reductase will use an NADPH as an electron donor to reduce the oxidised glutathione back into its working state.
- After giving up its electron, the NADPH will become NADP+.
- To replenish the supply of NADPH, the glucose-6-phosphate dehydrogenase enzyme, or G6PD, reduces NADP+ back to NADPH by oxidising a glucose-6-phosphate.
- Glucose-6-phosphate is a metabolite of glucose so we usually have a ready supply of this molecule as long as we are not in a starving state.
Define G6PD deficiency
G6PD deficiency is a condition where there is a defect in the G6PD enzyme normally found in all cells in the body.
What is the epidemiology of G6PD deficiency
- It is inherited in an X linked recessive pattern, meaning it usually affects males.
- It is more common in Mediterranean, Middle Eastern and African patients.
- 6DPD deficiency can be protective against malaria
What are the triggers for G6PD deficiency
- Fava beans
- Soy products
- Red wine
- Infections (viral hepatitis or pneumonia)
- Metabolic acidosis
- Medications:
- Primaquine (an antimalarial)
- Ciprofloxacin
- Nitrofurantoin
- Trimethoprim
- Sulfonylureas (e.g gliclazide)
- Sulfasalazine and other sulphonamide drugs
Describe the pathophysiology of G6PD deficiency
G6PD deficiency is caused by mutations on the G6PD gene which is found on the X chromosome and thus it’s an X-linked recessive genetic condition and it almost exclusively manifests as a disease in men.
The G6PD mutations cause defective G6PD enzymes to be produced that have a shorter half-life. There are two common types of G6PD deficiency: a Mediterranean and an African variant.
Low levels of G6PD causes low levels of NADPH, leading to low levels of reduced glutathione.
G6PD is the only way for red blood cells to get NADPH so they are especially susceptible to damage caused by free radicals.
When these build up, it causes the cell membrane to become unstable, causing haemolysis.
Free radicals can also directly damage haemoglobin molecules which are the oxygen carrying protein in red blood cells. These damaged proteins precipitates inside the cells and are called Heinz bodies.
The spleen macrophages notice these Heinz bodies and try to remove them by taking a chunk out of the cells, leaving these red blood cells partially devoured. These are known as bite cells.
When haemolysis occurs, this leads to conversion to bilirubin, which can result in jaundice and further complications e.g. gallstones. Some of the bilirubin is converted to urobilin, which builds up to give the urine a dark tea-like colour. This could cause damage to the kidneys.
What are triggers for G6PD deficiency
Periods of increased stress, with a higher production of ROS, can lead to acute haemolytic anaemia.
e.g. infections (viral hepatitis or pneumonia), metabolic acidosis, fava beans, soy products, red wine, certain medications
What are the clinical manifestations of G6PD deficiency
- Signs
- Jaundice
- Pallor
- Splenomegaly
- Dark tea-like coloured urine
- Symptoms
- Shortness of breath
- Fatigue
- Dizziness
- Headaches
- Palpitations
What are the investigations for G6PD deficiency
- FBC: low levels of RBC, high reticulocytes
- Blood film: heinz bodies and bite cells
- LDH: elevated
- Bilirubin: elevated
- Haptoglobin: low
- Coomb’s test: negative (used to detect immune mediated anaemias)
- Diagnosis can be made by doing aG6PD enzyme assay
What is the management for G6PD deficiency
- Avoid trigger of haemolysis e.g. fava beans and certain medications
- In certain cases, transfusions may be needed
What are the complications with G6PD deficiency
- Gallstones: due to jaundice
- Kidney damage
Define aplastic anaemia
Aplastic anaemia is a stem cell disorder characterised by pancytopenia.
This means there is anaemia, leukopenia, and thrombocytopenia.
It is usually an acquired condition but may be inherited
Describe the aetiology of aplastic anaemia
- Idiopathic (most common)
- Radiation and toxins
- Drugs e.g. certain chemotherapeutic agents, anti-seizure medication, anti-inflammatory medications, anti-thyroid medications and certain antibiotics
- Infections e.g. HIV, EBV
- Clonal or genetic disorders e.g. Fanconi’s anaemia
Describe the pathophysiology of aplastic anaemia
- The most common cause of aplastic anaemia is autoimmune destruction of haematopoietic stem cells.
- Research shows that there are alterations in the immunologic appearance of haematopoietic stem cells because of genetic disorders, or after exposure to environmental agents, like radiation or toxins.
- This means that the hematopoietic stem cells start expressing non-self antigens and the immune system subsequently targets them for destruction.
Describe the clinical manifestations of aplastic anaemia
- Signs
- Pallor
- Symptoms
- Fatigue
- Palpitations
- Dizziness
- Headaches
- Chest pain and shortness of breath: as heart works harder to compensate for low RBC count
- Increased bleeding and petechiae: due to thrombocytopenia
- Recurrent infections: due to leukopenia
Describe the investigations for aplastic anaemia
- FBC: anaemia, leukopenia, thrombocytopenia, low reticulocyte count
- Erythropoietin: may be raised to try and compensate for low RBC
- Bleeding time: increased
- Bone marrow biopsy: shows low counts of haematopoietic stem cells
Describe the management for aplastic anaemia
- Removal/ treatment of causes e.g. drugs or infections
- Transfusions
- Stem cell transplant
- Immunosuppressive treatment
What are the 4 major globin chain types
Haemoglobin is made up of four globin chains, each bound to a heme group.
There are four major globin chain types - alpha (α), beta (β), gamma (γ), and delta (δ).
These four globin chains combine in different ways to give rise to different kinds of haemoglobin.
Blood consists of HbA, HbA2 and HbF.
HbS is when Hb contains 2 alpha chains and 2 mutated beta chains.
Define sickle cell anaemia
Sickle cell anaemia is an autosomal recessive mutation in the beta chain of haemoglobin, resulting in sickling of red blood cells (RBCs) and haemolysis.
Describe the epidemiology of sickle cell anaemia
The prevalence of sickle cell trait in sub-Saharan Africa is the highest in the world. This may be because it is protective against malaria.
Describe the risk factors for sickle cell anaemia
- African: 8% of black people carry the sickle cell gene
- Family history: autosomal recessive pattern
- Triggers of sickling: dehydration, acidosis, infection, and hypoxia
- GENETIC
Why are neonates with sickle cell disease often asymptomatic for the first 4-6 months
Neonates with sickle cell disease are often asymptomatic for the first 4-6 months of life due to high levels of HbF (foetal haemoglobin), which is protective against sickling due to its high oxygen affinity. Over time, as HbF falls and HbS predominates, patients eventually become symptomatic.
Describe the pathophysiology of sickle cell anaemia
Under physiological stress, sickled haemoglobin (HbSS) polymerises and caused erythrocytes to deform into a sickled shape. Stressors are: hypoxia, acidosis, infection, cold temperatures, dehydration. Deformed RBCs may cause vaso-occlusion or slow the blood flow.
Repeated sickling of RBCs damages the cell membrane and promotes premature haemolysis, causing anaemia. Bone marrow and liver compensate for haemolysis by produces more RBCs, causing bone deformities and hepatomegaly
What are chronic symptoms of sickle cell anaemia
- Pain
- Related to anaemia: fatigue, dizziness, palpitations
- Related to haemolysis: jaundice, and gallstones
What are the acute symptoms of sickle cell anaemia due sequestration crisis
- RBCs sickle in the spleen, causing pooling of blood and a rapid drop in Hb and platelets
- Abdominal painsecondary to massive splenomegaly, possibly with hypovolaemic shock
- Autosplenectomy: repeated episodes lead to splenic infarction, fibrosis, and atrophy.
What are the acute symptoms of sickle cell anaemia due to aplastic crisis
- Infection withparvovirus B19causes bone marrow suppression
- Sudden onsetpallor, fatigue, and anaemia
- Differentiated from sequestration as it usually causes anaemia withreducedreticulocyte count andno splenomegaly
What are the acute symptoms of sickle cell anaemia due to haemolytic crisis
Increased rate of intravascular and extravascular haemolysis; rare
What are the acute symptoms of sickle cell anaemia due to vaso-occlusive crisis
Painful, vaso-occlusive episodes occur as RBCs sickle in various organs
- Bone
- Dactylitis: inflammation of digits
- Avascular necrosis: death of bone tissue due to a lack of blood supply
- Osteomyelitis: most commonly due to salmonella
- Lungs
- Acute chest syndrome:severe and potentially life-threatening
- Dyspnoea
- Chest pain
- Hypoxia
- Pulmonary infiltrates on chest X-ray
- Acute chest syndrome:severe and potentially life-threatening
- Spleen
- Autosplenectomy
- Patients are at risk of infection from encapsulated bacteria
- CNS
- Stroke
- Kidney
- Renal papillary necrosis
- Genitalia
- Priapism: painful prolonged erection
What are the primary investigations for sickle cell anaemia
- Newborn screening with Guthrie heel prick:sickle cell anaemia is one of a number of conditions screened for in all neonates in the UK at 5 days of age
- FBC:normocytic anaemia with reticulocytosis
- Blood film:sickled RBCs, target cells, Howell-Jolly bodies (RBC nuclear remnants seen later in the disease due to hyposplenism)
- Hb electrophoresis and solubility: diagnosticinvestigation, demonstratingincreased HbS (2 alpha chains and 2 abnormal beta chains) and reduced/absent HbA (α2β2)
What are the investigations for an acute crisis for sickle cell anaemia
- Bedside
- Urinary Legionella/Pneumococcal antigen:in chest crisis
- Sputum culture and sputum/nasopharyngeal aspirate: in chest crisis
- Bloods
- ABG: if SpO2 < 94%
- FBC: normocytic anaemia, generally reticulocytosis; aplastic crisis causes reduced reticulocytes
- U&Es and LFTs
- G&S and crossmatch: in case of transfusion
- Blood cultures: in all febrile patients with chest crisis
- Serology(atypical respiratory organisms): in chest crisis
- Imaging
- CXRpulmonary infiltrates in chest crisis
- Bone X-ray:if suspecting osteomyelitis or dactylitis
What is the acute management for sickle cell anaemia
Acute management depends on which type of complication has occurred.
- Analgesia:patients often require opiates or patient-controlled analgesia
- Hydration:dehydration precipitates sickling so it is important that patients are well hydrated
- Oxygen:used if hypoxic or there is evidence of chest crisis
- Antibiotics:used in chest crisis or if evidence of infection, e.g. osteomyelitis
- Blood transfusion:in a severe crisis, a blood transfusion reduces the proportion of HbS and is often required in a chest crisis
- Exchange transfusion: involves removal of HbS in exchange for normal Hb in a life-threatening crisis, for example, a severe chest crisis or stroke
- Penile aspiration: in priapism
What is the long term management for sickle cell anaemia
Chronic management is largely supportive and aimed at preventing infections and sickle crises, as well as managing anaemia.
- Pain management:regularly prescribed medications to manage chronic pain
- Hydroxycarbamide: increases the level of HbF, which is protective against sickling and reduces the frequency of crises and blood transfusions
- Lifelong phenoxymethylpenicillin: patients are at risk of infection from encapsulated bacteria due to hyposplenism from autosplenectomy. Lifelong penicillin V prophylaxis for patients with sickle cell disease, starting from 3 months old, is required
- Regular vaccinations: pneumococcal polysaccharide vaccine every 5 years and yearly influenza
- Blood transfusion
- Iron chelation: to prevent iron overload from blood transfusions
- Folic acid supplementation: offered to all patients as it raises haemoglobin levels
- Bone marrow transplant: could be curative
What are the complications with sickle cell anaemia
- Sickle cell crises
- Anaemia
- Increased risk of infection
What is the prognosis for sickle cell anaemia
Prognosis is variable. The median age at death is 40-50 for patients with sickle cell disease, with a third of patients dying during an acute crisis
Describe the absorption of vitamin B12
- Vitamin B12, also known as cobalamin, is a complex organometallic compound found in animal and dairy products like meat, eggs or milk
- Dairy and animal products are broken down in the stomach by pepsin, to release B12
- Intrinsic factor, made by parietal cells, can bind to B12, and the B12-intrinsic factor complex passes into the intestines
- When the complex reaches the terminal ileum, the enterocytes recognise intrinsic factor and absorb the whole complex
- Inside the enterocytes, intrinsic factor gets removed and a protein called transcobalamin-II binds the free B12 and transports it into the blood and from there, to various target tissues
- Some of the transcobalamin-B12 complex gets to the liver, where B12 can be stored for several years
Define B12 deficiency anaemia
Anaemia (low levels of Hb in the blood) caused by B12 deficiency.
This is a macrocytic megaloblastic anaemia.
Describe the epidemiology of B12 deficiency anaemia
- Vitamin B12 is predominantly found in meat and dairy products (due to bacterial synthesis) and is not present in plants. Thus, dietary deficiency is uncommon and typically seen in strict vegans.
- Vitamin B12 deficiency increases with age.
- Unlike folate, vitamin B12 stores last for years before deficiency develops.
- B12 deficiency most commonly due to pernicious anaemia
- Pernicious anaemia: relatively common amongst Northern Europeans, with a high prevalence in those aged 60-70 years old
- F>M
Describe the pathophysiology of B12 deficiency anaemia
- Vitamin B12 (cobalamin) is found in meats and diary products. It is an essential vitamin for DNA synthesis in cells undergoing rapid proliferation.
- Deficiency of Vitamin B12 affects rapidly dividing cells, such as those in the bone marrow. This can lead to pancytopenia. As compensation for anaemia, the bone marrow produces abnormal precursors of RBCs - macrocytic, megaloblastic RBCs
- Other cells that are affected include rapidly dividing mucosal epithelium cells of the tongue, causing glossitis.
- Vitamin B12 also plays a role in keeping levels of methylmalonic acid low. This is a harmful substance that can cause neurological damage.
- Neurological features:
- Peripheral neuropathy
- Subacute degeneration of the cord
- Focal demyelination
- Neurological features:
What are the causes of vitamin B12 deficiency
- Causes of vitamin B12deficiency include:
- Inadequate intake(e.g. strict vegetarians, vegans)
- Inadequate secretion of intrinsic factor(e.g. pernicious anaemia, gastrectomy)
- Malabsorption(e.g. Crohn’s, tropical sprue, patients who have had gastric bypass)
- Inadequate release of B12from food(e.g. gastritis, alcohol abuse)
Describe the clinical manifestations of B12 deficiency anaemia
- Signs
- Pallor
- Signs of neurological deficit e.g. confusion, ataxia etc
- Symptoms
- Shortness of breath
- Fatigue
- Palpitations
- Headaches
- Glossitis
- CNS involvement
- Personality change
- Depression
- Memory loss
- Visual disturbances
- Numbness, weakness and paraesthesia affecting the lower extremities
- Ataxia
- Loss of vibration sense or proprioception
- Autonomic dysfunction (e.g. bladder/bowel dysfunction)
Describe the first line investigations for B12 deficiency anaemia
- Full blood count (FBC): raised MCV
- Blood film: megaloblastic anaemia +/- hypersegmented neutrophils
- Haematinics: look for iron, B12, folate deficiency
- Lactate dehydrogenase (LDH): may be elevated
- Liver function tests (LFTs)
What further investigations may be done for B12 deficiency anaemia
- Bone marrow aspirate: megaloblastic erythropoiesis, marked erythroid hyperplasia with ineffective erythropoiesis with the development of giant metamyelocytes
- Investigations to identify the underlying cause e.g.
- Schilling’s test: to test for pernicious anaemia; radiolabelled B12 given and absorption measured. Later repeated with IF administration to see if B12 absorption increases
- Serological assessment e.g. autoantibodies seen in pernicious anaemia
- Gastroscopy
What is the management for B12 deficiency anaemia
- Treatment of the underlying cause
- B12 supplementation e.g. oral cyanocobalamin; intramuscular hydroxocobalamin
Define folate deficiency anaemia
Anaemia (low levels of Hb in the blood) caused by folate (vitamin B9) deficiency. This is a type of macrocytic megaloblastic anaemia.
Describe the epidemiology of folate deficiency anaemia
- In general, megaloblastic anaemia and folate deficiency are seen most commonly in countries where malnutrition is problematic.
- High-risk patient groups include: children, pregnant women and the elderly.
What are the risk factors for folate deficiency anaemia
- Elderly
- Poverty
- Alcoholic
- Pregnant
- Crohn’s or coeliac disease
Describe the pathophysiology of folate deficiency
- Folate (vitamin B9) is another important molecule which acts as a cofactor in amino acid metabolism and DNA/RNA synthesis.
- This DNA impairment will affect all cells, but bone marrow is most affected since its the most active in terms of cell division. This means that folate deficiency can eventually lead to pancytopenia. In response to the anaemia, the bone marrow compensates by releasing megaloblasts into the blood - and the final result is macrocytic, megaloblastic anaemia.
- Other rapidly dividing cells, include mucosal epithelial cells of the tongue. These are affected, preventing healing. This leads to glossitis.
- Folate is also essential for foetal development - deficiency can result in neural tube defects e.g. spina bifida. So supplementation is essential during pregnancy!
- Folate is commonly found in a variety of food sources.
- Absorption of folate occurs within the proximal part of the small intestines (e.g. duodenum & jejunum).
- There are plenty of hepatic stores of folate (approx. 8-20 mg), but this reserve is lost rapidly from cellular metabolism and the shedding of epithelial cells. There is an estimated loss of 1-2% of stores per day. Therefore, folate deficiency can develop after months, compared to vitamin B12 deficiency, which tends to develop over years.
What are causes of folate deficiency
- Inadequate intake
- Malabsorption(e.g. coeliac disease, resection)
- Increased requirements(e.g. pregnancy, malignancy disease)
- Increased loss(e.g. Chronic liver disease)
- Other(e.g. anti-convulsants, alcohol abuse)
What are the clinical manifestations of folate deficiency anaemia
- Signs
- Pallor
- Symptoms
- Fatigue
- Dyspnoea
- Palpitations
- Headache
- Glossitis
- Features of pancytopenia e.g. excessive bleeding and bruising due to thrombocytopenia, recurrent infections due to leukopenia
- Symptoms of underlying cause e.g.
- Coeliac disease: diarrhoea, bloating, dyspepsia and abdominal discomfort.
What are the primary investigations for folate deficiency anaemia
- Primary investigations
- FBC: high MCV
- Blood film: macrocytic, megaloblastic RBC
- Haematinics: search for iron, B12 and folate deficiencies
- Serum and red cell folate: low
What other investigations might be done for folate deficiency anaemia
GI investigation e.g. small bowel biopsy to exclude occult GI disease
What is the management for folate deficiency anaemia
- Treat underlying cause e.g. stopping drugs or alcohol consumption
- Folic acid supplements: always give alongside B12, because replacement of folic acid in the presence of vitamin B12 deficiency may cause significant neurological disease.
Where does all of the blood end up
In the superior or inferior vena cava and then dumps into the right atrium. From there, the blood goes into RV is pumped into the PA and eventually oxygenated in the lungs.
Describe the platelet plug formation/ primary haemostasis
The process starts with damage to the endothelium or inner lining of blood vessel walls, after which there’s an immediate vasoconstriction or narrowing of the blood vessel, limiting the amount of blood flow.
After that, some platelets adhere to the damaged vessel wall, and become activated by collagen and tissue factor.
These platelets then recruit additional platelets forming a plug. This is called primary haemostasis.
Describe the coagulation cascade/ secondary haemostasis
After that, the coagulation cascade is activated. A set of clotting factors that are made by the liver and are inactive, get proteolytically cleaved.
This active protein begins a chain reaction, proteolytically cleaving and activates the next clotting factor and so on.
The final step is activation of the protein fibrinogen to fibrin, which deposits and polymerises to form a mesh around the platelet plug. This process is known as secondary haemostasis.
What clotting factors do antithrombin and protein S inactivate
The activation of the cascade is carefully controlled by anticoagulation proteins that target and inactivate key clotting factors. For example, antithrombin inactivates Factors IXa, Xa, XIa, XIIa, VIIa and thrombin, while protein S inactivates Factors Va and VIIIa.
What are D-dimers
As the clot grows in size, it limits the amount of blood able to pass through, increasing the pressure in that vein.
In most cases, the clot starts naturally breaking down: for example, enzymes like plasmin break down fibrin into fragments called D-dimers.
Define deep vein thrombosis
A deep vein thrombosis (DVT) is the formation of a blood clot in the deep veins of the leg or pelvis (as opposed to the superficial veins).
Describe the epidemiology of a DVT
- DVT is a very common medical condition, with the incidence increasing with age.
- 65% of below-knee DVTs are asymptomatic and these rarely embolise to the lung
What are the risk factors for a DVT
- Age: the risk of DVT is greater after 40 years old
- Smoking
- Drugs: combined oral contraceptive pill, hormone replacement therapy, tamoxifen
- Immobility: surgery, hospitalisation, long-haul travel and bed-bound
- Pregnancy
- Trauma
- Malignancy
- Polycythaemia
- SLE
- Thrombophilia e.g. antiphospholipid syndrome, antithrombin deficiency, protein C or S deficiency, Factor V Leiden
- Virchow’s triad: hypercoagulability, venous stasis, endothelial damage
Describe normal blood flow
Blood flow is normally laminar and ensures platelets and clotting factors are dispersed and not activated. Stasis disrupts this and promotes thrombus formation; immobility and polycythaemia
What are the clinical manifestations of a DVT
- Signs
- Unilateral swelling
- Oedema
- Tender and erythematous
- Distention of superficial veins
- Phlegmasia cerulea dolens: occurs in a massive DVT, resulting in obstruction of venous and arterial outflow (rare). This leads to ischaemia and a blue and painful leg
- Symptoms
- Unilateral calf pain, redness and swelling
What is the Wells score and what are the criteria of it
The Wells score calculates the risk of DVT and determines how the patient is investigated and managed. Those with a score ≥ 2 are deemed high risk.
Active cancer +1
Bedridden or recent major surgery +1
Calf swelling > 3cm compared to other leg +1
Superficial veins (non-varicose) present +1
Entire leg swollen +1
Tenderness along veins +1
Pitting oedema of the affected leg +1
Immobility of affected leg e.g. plaster +1
Previous DVT +1
Alternative diagnosis likely -2
What examinations may be done for possible DVT
Examination: measure the circumference of the calf 10cm below the tibial tuberosity. More than 3cm difference between calves is significant.
What tests may be done if Wells score is >=2
Duplex ultrasound of leg within 4 hours: this is diagnostic (offer a D-dimer if the scan is negative); if an ultrasound is not possible to arrange within 4 hours:
- Perform a D-dimerAND
- Offer interim anticoagulation for 24 hours (ideally in a form that can be easily continued)AND
- Arrange the ultrasound for the following day
What tests might be done if Wells score <=1
D-Dimer with a result available within 4 hours: if D-Dimer results cannot be obtained within 4 hours, offer interim anticoagulation until the result is available
- If D-Dimer is raised: perform a duplex ultrasound within 4 hours
- If D-Dimer is normal: a DVT is unlikely and alternative diagnoses should be considered
