Haematology Flashcards
What is the lifespan of a red blood cell?
120 days
What is meant by the reticulocyte count?
Count of immature RBC’s in the bone marrow. Low reticulocyte count indicates RBC production is an issue.
Why is Hb high in a dehydrated patient?
Reduction in plasma volume leads to a falsely high Hb.
What is meant by hypochromic?
Pale red blood cells.
What is meant by microcytic?
Low mean corpuscular volume.
What is meant by normocytic?
Normal mean corpuscular volume.
What is meant by macrocytic?
High mean corpuscular volume.
What causes microcytic anaemia?
- iron deficiency
- thalassaemia
- anaemia of chronic disease
- sideroblastic anaemia (bone marrow cannot produce normal RBCs despite normal iron)
What is meant by megaloblastic anaemia?
Large immature red blood cells.
What causes megaloblastic anaemia?
Vitamin B12 or folate deficiency.
What are some causes of normoblastic macrocytic anaemia?
- alcohol
- increased reticulocytes due to haemolysis / haemorrhage
- liver disease
- hypothyroidism
- certain drug therapies
What are some causes of normocytic anaemia?
- acute blood loss
- anaemia of chronic disease
- CKD
- autoimmune rheumatic disease
- marrow infiltration / fibrosis
- endocrine disease
- haemolytic anaemia
What are some compensatory changes that occur in response to anaemia?
- increased tissue perfusion
- increased O2 transfer to tissues
- increased RBC production
What are some pathological consequences of anaemia?
- myocardial fatty change
- fatty change in liver
- aggravates angina and claudication
- skin and nail atrophic changes
- CNS cell death
What are some symptoms of anaemia?
- fatigue
- headaches
- faintness
- dyspnoea
- angina
- anorexia
- intermittent claudication
- palpitations
What are some signs of anaemia?
- pallor
- tachycardia
- systolic flow murmur
- cardiac failure
How are iron ions absorbed?
- actively transported into duodenal intestinal epithelial cells by haem transporter HCP1
How are iron ions stored?
- some is incorporated into ferritin (intracellular iron store)
- remainder stored as haemosiderin (found in macrophages in the bone marrow, liver and spleen)
What happens to iron ions that are not stored?
- released into the blood bound to transferrin and transported to the bone marrow
- majority of iron is incorporated into haemoglobin
What is meant by poikilocytosis?
An increase in RBCs of abnormal shape.
What is meant by anisocytosis?
Variation in RBC size.
How is vitamin B12 absorbed?
Binds to intrinsic factor and is then absorbed in the terminal ileum.
Where is intrinsic factor produced?
Parietal cells of the stomach.
Why can mild jaundice occur in pernicious anaemia?
Due to the increased haemolysis as the body attempts to get rid of macrocytic RBCs.
What size RBC are found in haemolytic anaemia?
- normocytic
- macrocytic (due to there being large young RBCs as a result of excessive destruction of old RBCs)
Where can haemolysis occur?
- circulation
- reticuloendothelial system (macrophages in the liver and spleen)
- bone marrow
What happens when haemolysis occurs in the circulation?
- liberated haemoglobin initially binds to haptoglobin but these quickly become saturated
- excess free haemoglobin is filtered by the glomerulus and excreted in urine
- small amounts of Hb are reabsorbed into renal tubular cells where it is broken down and deposited in the cells as haemosiderin
What is meant by compensated haemolytic disease?
- red cell loss is contained within the bone marrow’s capacity to increase output
- bone marrow expands the volume of active marrow and undergoes erythroid hyperplasia
Why might haemolytic anaemia be macrocytic?
Macrocytic reticulocytes are released prematurely from bone marrow.
What are the main causes of haemolytic anaemia?
- hereditary spherocytosis
- G6PD deficiency
- beta / alpha thalassaemia
- sickle cell disease
- autoimmune haemolytic anaemia
What are some features of haemolytic anaemia?
- high serum unconjugated bilirubin
- high urinary urobilinogen
- high faecal stercobilinogen
- splenomegaly
- bone marrow expansion
- reticulocytosis
How is Hodgkins lymphoma histologically different from non-Hodgkin’s lymphoma?
Presence of Reed-Sternberg cells in Hodgkin’s lymphoma.
Findings of Auer rods indicates?
Acute myeloid leukaemia.
Risk factors for DVT?
- pregnancy
- recent surgery
- recent leg fracture
- recent history of cancer
- immobility
- HRT / oestrogen-containing contraception
Most common cause of malaria?
Plasmodium falciparum
Gold standard treatment for thrombotic thrombocytopenic purpura?
Plasma exchange
What is the Well’s score?
DVT / PE risk scoring.
What staging system is used for HL and NHL?
Ann Arbor
What are B symptoms?
- fever
- night sweats
- weight loss of > 10% of body weight over 6 months.
Examples of LMWH?
- dalteparin
- enoxaparin
Mechanism of action of fondaparinux?
Factor Xa inhibitor.
Mechanism of action of dalteparin / enoxaparin?
- binds to and potentiates antithrombin III
- this forms a complex that irreversibly inactives factor Xa and inhibits thrombin (IIa)
Examples of DOACs?
- dabigatran
- rivaroxaban
- apixaban
Mechanism of action of dabigatran?
Thrombin inhibitor.
Mechanism of action of rivaroxaban / apixaban?
Factor Xa inhibitor.
What is the protein target of rituximab?
CD20
First line treatment for severe / complicated malaria?
IV artesunate
What is the most common form of anaemia?
Iron-deficiency anaemia.
What are the four categories of causes of IDA?
- inadequate dietary intake
- impaired iron absorption
- increased iron loss
- increased iron requirement
Examples of causes of impaired iron absorption?
- achlorhydria
- gastric surgery
- coeliac disease
- H. pylori infection
Examples of causes of increased iron loss?
- GI bleeding (haemorrhoids, peptic ulcer disease, IBD)
- menorrhagia
Examples of causes of increased iron requirement?
- young children
- pregnancy
- lactation
Where does iron absorption mostly occur?
Duodenum and proximal jejunum.
Iron transport molecule?
Transferrin
Iron storage molecule(s)?
Ferritin and haemosiderin.
What is hepcidin?
Hormone that decreases intestinal iron absorption and prevents iron recycling.
What causes increased hepcidin transcription?
Systemic inflammatory / infectious states.
Appearance of RBCs in IDA?
Hypochromic and microcytic.
Symptoms of IDA? (8)
- dyspnoea (on exertion)
- fatigue
- headache
- cognitive dysfunction / impaired concentration
- syncope
- irritability
- palpitations
- angina
Signs of IDA? (6)
- pallor (& conjunctival pallor)
- atrophic glossitis
- dry skin
- dry / damaged hair
- angular stomatitis
- nail changes (longitudinal ridges, koilonychia)
What is atrophic glossitis?
Loss of filiform papillae on the dorsal surface of the tongue.
What is angular stomatitis?
Ulceration at the corners of the mouth.
What is kolionychia?
Spoon shaped nails.
What is seen on a peripheral blood smear in IDA?
- hypochromic & microcytic cells
- anisopoikilocytosis - size and shape variation
- pencil cells
What happens to total iron binding capacity in IDA?
Increases
Investigations for IDA? (6)
- FBC
- folate and B12
- peripheral blood smear
- blood cultures
- endoscopy
- coeliac serology
Oral iron supplement examples?
- ferrous sulphate
- ferrous fumarate
- ferrous gluconate
Adverse effects of oral iron?
- constipation / diarrhoea
- epigastric pain
- nausea
When would you give a blood transfusion for IDA?
Cardiovascular compromise - dyspnoea at rest, chest pain, lightheadedness.
Summary of IDA management?
- oral (or parenteral) iron supplementation
- blood transfusion if indicated by cardiovascular compromise
Most frequent cause of megaloblastic anaemia?
B12 / folate deficiency.
What is meant by megaloblastic anaemia?
Macrocytic anaemia, where the cells are immature due to defective DNA synthesis.
Most common cause of B12 deficiency?
Pernicious anaemia
Causes of B12 deficiency?
- pernicious anaemia
- gastrectomy
- congenital IF deficiency
- malabsorption (IBD, coeliac disease, etc)
- malnutrition
- drugs (PPIs, H2 receptor antagonists)
Which drugs can cause folate deficiency?
- methotrexate
- trimethoprim
- sulfasalazine
Causes of folate deficiency?
- drugs
- increased folate requirements (malignancy, pregnancy & lactation)
- malabsorption
- malnutrition
How is B12 absorbed?
- B12 is released from food by gastric acid
- free B12 binds to intrinsic factor
- the IF-B12 complex is absorbed in the terminal ileum
Which cells secrete intrinsic factor?
Parietal cells
Symptoms of B12 deficiency?
neurological problems - muscle weakness, loss of cutaneous sensation, pyschiatric disturbances
Signs and symptoms of B12 / folate deficiency anaemia?
- same as IDA (dyspnoea, headache, lethargy, palpitations, angular stomatitis, atrophic glossitis, etc)
- PLUS neurological problems (B12 deficiency)
Management of B12 deficiency?
- IM hydroxocobalamin
- dietary advice
What is cobalamin?
vitamin B12
Management of folate deficiency?
CHECK FOR B12 DEFICIENCY - folic acid treatment may mask B12 deficiency and allow progression to neurological disease development.
Oral folic acid (5mg daily) and dietary advice.
Neonatal complications of folate deficiency?
- neural tube defects
- prematurity
What is sickle cell anaemia?
Autosomal recessive condition causing sickle shaped RBCs.
Why does sickle cell anaemia result in haemolysis?
Sickle cells are fragile and easily destroyed, resulting in haemolytic anaemia.
HbS is the result of?
A single gene defect in the beta chain of haemoglobin.
What is meant by sickle cell trait?
A person has one copy of the sickle cell gene. They are usually asymptomatic.
What is the single gene mutation in sickle cell anaemia?
Valine replaces glutamic acid at the 6th amino acid of the beta globin chain.
When is fetal Hb replaced by adult Hb?
Around 6-12 months of age.
What causes the sickle shape of RBCs?
HbS polymerises with the RBC, forming long stiff fibres which result in the sickle shape.
What triggers polymerisation of HbS?
Hypoxia & acidosis.
What are some precipitating factors for vaso-occlusive episodes in sickle cell anaemia?
- acidosis
- dehydration
- cold temperatures
- stress
- infection
- extreme exercise
What are some clinical manifestations of sickle cell anaemia?
- vaso-occlusive crises
- dactylitis
- acute chest syndrome
- bone pain
- failure to thrive
- jaundice
- pallor, tachycardia and lethargy
What is meant by acute chest syndrome?
Caused by sickling of RBCs within the pulmonary vasculature. Presents like pneumonia (chest pain, fever, tachycardia, dyspnoea, etc).
Triggers for acute chest syndrome?
- thrombosis
- infection
- atelectasis
What causes bone pain in sickle cell anaemia?
Infarction and avascular necrosis due to vaso-occlusive crisis.
What is meant by splenic sequestration?
Life-threatening complication of sickle cell anaemia in children. Sickle cells obstruct a draining vein, causing RBCs to become trapped in the spleen.
What are some complications of sickle cell anaemia? (6)
- stroke
- avascular necrosis
- priapism
- chronic kidney disease
- acute chest syndrome
- increased susceptibility to infection
What is priapism?
Persistent and painful erection.
How is sickle cell anaemia screened for?
- newborn heel prick test
- genetic testing during pregnancy (in at-risk patients)
Investigations for sickle cell anaemia complications?
X-rays of long bones - infarction / avascular necrosis.
CXR - acute chest syndrome shows pulmonary infiltrate.
Summary of sickle cell disease management?
- avoid triggers
- genetic counselling
- pain management
- hydroxycarbamide stimulates HbF production
- blood transfusion / bone marrow transplant
- prevention and management of infections & complications
What is meant by haemolytic anaemia?
Anaemia secondary to the reduced survival of RBCs (lifespan < 100 days).
Examples of inherited haemolytic anaemias?
- metabolic abnormalities (G6PD deficiency)
- Hb abnormalities (sickle cell anaemia, thalassemia)
- membrane abnormalities (hereditary spherocytosis)
Examples of acquired haemolytic anaemias?
- autoimmune
- mechanical trauma
- infections (malaria)
- hypersplenism
Inheritance pattern of hereditary spherocytosis?
autosomal dominant
How does hereditary spherocytosis result in haemolysis?
- mutations lead to defects in the RBC membrane and cytoskeleton instability
- the resulting spherocytes are fragile and selectively removed by the spleen for destruction
Inheritance pattern of glucose-6-phosphate dehydrogenase deficiency?
X linked recessive
How does G6PD deficiency result in haemolysis?
- G6PD is important for NADPH generation
- NADPH helps scavenge oxidative metabolites that would cause damage to the RBC
Symptoms & signs of haemolytic anaemia?
- fatigue
- dyspnoea
- paraesthesia
- atrophic glossitis
- pallor
- splenomegaly
- jaundice
- dark urine
Investigations for haemolytic anaemia? (5)
- FBC
- blood film
- LFTs
- DAT test
- Hb electrophoresis
What FBC findings are present in haemolytic anaemia?
- normocytic anaemia
- increased reticulocyte count
Haptoglobin levels in haemolytic anaemia?
- may be elevated as it is an acute phase reactant
- may be decreased due to removal of Hb-haptoglobin complexes once haptoglobin has mopped up free Hb
What is the DAT test?
- direct antiglobulin test
- also known as the Coombs test
- detects antibodies on the surface of RBCs
- to investigate an autoimmune cause of haemolysis
What is meant by pernicious anaemia?
Autoimmune condition affecting the parietal cells of the stomach, resulting in B12 deficiency anaemia due to intrinsic factor deficiency.
What is the pathophysiology of pernicious anaemia?
Autoantibodies form against parietal cells / intrinsic factor.
This leads to a lack of intrinsic factor, preventing B12 absorption.
Investigations for pernicious anaemia?
- B12 deficiency anaemia investigations
- intrinsic factor antibody
- parietal cell antibody
Management of pernicious anaemia?
IM hydroxycobalamin
What is meant by anaemia of chronic disease?
Syndrome in which anaemia is the result of an inflammation-mediated reduction in RBC production and survival.
What size and colour RBCs are found in anaemia of chronic disease?
Normocytic normochromic / microcytic hypochromic.
Causes of anaemia of chronic disease?
- infection
- neoplasm
- autoimmune disease
- trauma
- major surgery
Pathophysiology of anaemia of chronic disease?
- underlying condition causes the release of pro-inflammatory cytokines
- triggers upregulation of hepcidin
- serum iron levels fall, resulting in decreased erythropoiesis
- survival of circulating RBCs may be decreased due to damage by free radicals generated by cytokines, or increased erythrophagocytosis
What is the function of hepcidin?
Negative regulator of free iron:
- causes iron trapping in macrophages
- decreases iron absorption from the GI tract
- causes splenic sequestration of iron
- causes impaired bone marrow responsiveness to EPO
How is anaemia of chronic disease managed?
- treat underlying disease
- iron supplementation in patients with iron deficiency
- RBC transfusion in severe anaemia
- erythropoiesis-stimulating agents may be used if tranfusion is unsuitable
What is meant by deep vein thrombosis?
Formation of a thrombus that develops in one of the deep veins, characteristically occurring within the lower limb.
What is meant by distal DVT?
Below the popliteal trifurcation.
Distal DVT prognosis?
Likely to resolve spontaneously without symptoms.
What is meant by proximal DVT?
Above the popliteal trifurcation - may affect the popliteal, femoral, or iliac veins.
Proximal DVT prognosis?
50% of symptomatic patients develop PE within 3 months.
Provoked vs unprovoked DVT?
Provoked - DVT occurs within 3 months of exposure to transient / persistent risk factors.
Unprovoked - no readily identifiable risk factor for DVT.
Intrinsic risk factors for DVT?
- Hx of DVT
- cancer
- obesity
- thrombophilia
- varicose veins
- smoking
- older age
- male sex
Transient risk factors for DVT?
- hospitalisation
- recent major surgery / trauma
- immobility
- oestrogen-containing hormone therapy
- long-distance sedentary travel
- dehydration
- infection
- pregnancy (& up to 6 weeks post partum)
Components of Virchow’s triad?
- venous stasis
- hypercoagulable state
- endothelial injury
Symptoms and signs of DVT? (5)
- unilateral leg swelling (calf asymmetry)
- pain / tenderness in leg
- erythema
- warmth
- venous distention
What is the Wells score?
Scoring system used to assess risk of DVT / PE.
Investigations if Wells score is 1 or less?
- D-dimer
- ultrasound proximal leg veins if D-dimer positive
Investigations if Wells score is 2 or more?
- ultrasound proximal leg veins within 4 hours
- if delay is expected: request d-dimer, give anticoagulation, arrange ultrasound within 24 hours
Sensitivity and specificity of D-dimer?
High sensitivity - negative result excludes DVT.
Low specificity - cannot be used to make a positive diagnosis of DVT.
Gold standard investigation for DVT?
Ultrasound of proximal leg veins.
Management of DVT?
Anticoagulation:
- first-line DOAC (apixaban / rivaroxaban)
- LMWH is an alternative (dalteparin / enoxaparin)
Continue anticoagulation for at least 3 months.
How many cases of PE are preceded by DVT?
80%
Complications of DVT?
- PE
- post-thrombotic syndrome
What is post-thrombotic syndrome?
- chronic swelling, pain, and skin changes due to venous stasis secondary to venous hypertension
- may lead to ulcers and gangrene
What is acute myeloid leukaemia?
Haematological malignancy caused by clonal expansion of myeloid blasts in the bone marrow, peripheral blood, and extramedullary tissues.
Which age group is most commonly affected by AML?
Much more common in the over 60s
What is myelodysplastic syndrome?
Heterogeneous group of blood disorders affecting haematopoiesis. Increases risk of developing AML.
Risk factors for AML? (5)
- increasing age
- myelodysplastic syndrome
- congenital disorders (Down’s syndrome)
- radiation exposure
- previous chemotherapy
How does AML cause disease?
- uncontrolled proliferation of myeloid progenitor cells
- abnormal cells accumulate in the bone marrow, resulting in reduced production of normal cell lines
- spread and proliferation in other tissues
Signs and symptoms of AML?
- anaemia
- neutropenia (recurrent infections)
- thrombocytopenia
- lymphadenopathy
- hepatosplenomegaly
- bone pain
- violaceous skin deposits
- leucostasis
What is meant by leucostasis?
White cell plugs within the microvasculature. Presents with symptoms such as: altered mental state, headache, breathlessness, visual changes.
Gold standard investigation for AML?
Bone marrow aspirate and biopsy - shows a myeloid blast count of > 20%.
What is shown on a peripheral blood smear in AML?
Auer rods (azurophilic structures).
How is AML managed?
- cytoreduction with hydroxycarbamide
- tumour lysis syndrome prophylaxis
- chemotherapy
- allogenic stem cell transplant (generally after failure of other treatments)
What does tumour lysis syndrome prophylaxis involve?
- good hydration
- monitor electrolytes
- allopurinol to control hyperuricaemia
Tumour lysis syndrome definition?
Metabolic and electrolyte abnormalities occurring after the initiation of cancer treatment, due to the rapid breakdown of a large number of cancer cells. The subsequent release of large amounts of intracellular content overwhelms normal homeostatic mechanisms.
What is acute lymphoblastic leukaemia?
Haematological malignancy caused by acute proliferation of abnormal lymphoid progenitor cells.
Which age group does ALL most commonly affect?
75% of cases occur in children under 6.
Most common cancer in children.
Also affects older adults (>45).
Risk factors for ALL?
- young children / > 45 years
- radiation exposure
- genetic disorders (Down’s syndrome)
- previous chemotherapy
- family history
Pathophysiology of ALL?
- uncontrolled proliferation and clonal expansion of a genetically altered lymphoid progenitor cell
- bone marrow / extramedullary infiltration