Haematology Flashcards
Tell me the key facts about acute promyelocytic leukaemia.
A subtype of AML. Chromosomes 15 and 17 (exchange of material). Formation of PML-RAR alpha fusion gene. Cells formed commonly have Auer rods. Is a medical emergency you get coagulopathy (anticoagulation). Treatment is immediate all-transretinoic acid (ATRA) and then for 3 months after.
Which cell type produces platelets
Megakaryocyte
Where are blood cells made at the different stages of development?
Following conception - yolk sac
~12 weeks foetus - liver and spleen
Baby born- bone marrow primary responsible
In adults the bone marrow production is confined to the axial skeleton whereas in children the long bones also contribute
What is the classic site for bone marrow biopsy
Posterior superior iliac crest
What the ‘influencing’ factors for blood cell production i.e. production of granulocytes, platelets and red blood cells and where are they released from?
G-CSF which is most specific for neutrophils is released by the endothelium and macrophages
EPO- production of red blood cells- produced by kidneys in response to hypoxia or anaemia
TPO- production of platelets- produced by the liver
What are the values corresponding to microcytic, normocytic and macrocyctic anaemia?
Microcytic is <80
Normocytic is 80-100
Macrocytic is >100
If a blood film has lots of reticulocytes (young red cells) what is the term used to describe the blood film?
Polychromasia meaning ‘many colours’- reticulocytes are larger and more blue than normal cells
What is one of the first investigations done after discovering that a patient has an abnormal blood cell count?
Peripheral blood film
General features of acute leukaemia
Proliferation of immature cells. Differentiation block (stops the bone marrow from being able to produce normal healthy blood cells). Present with symptoms of marrow failure. Anaemia, thrombocytopenia (bleeding), neutropenia (infection). Patients have a very short history and are often unwell. An aggressive type of cancer.
General features of chronic leukaemia
Mature cells, less acute, often present with increased WCC. CML = chronic myeloid leukaemia (myeloproliferative): granulocytes. CLL = chronic lymphocytic leukaemia (lymphoproliferative): lymphocytes
Give the names of the other myeloproliferative neoplasms (other than CML).
Polycythaemia rubra Vera = raised red cells/ increased Hb and Hct
Essential thrombocythaemia = increased platelets only
Primary myelofibrosis = bone marrow fibrosis
What is the commonest mutation causing the myeloproliferative neoplasms?
JAK2
What age group does Hodgkin’s lymphoma more commonly occur?
Young adults
General difference between leukaemia and lymphoma?
Lymphoma is mainly in the lymph nodes, leukaemia is mainly in the blood and bone marrow
Which age group is ALL most common in?
Children
Which age group is CLL most common in?
The elderly
Myeloma can cause CRABI. Name the components
HyperCalcaemia Renal dysfunction Anaemia Bone (lytic lesions, osteoporosis, fractures) Infections
What is the classic bruising pattern seen in thrombocytopenia?
Petechiae (pin-prick bruises) is classic platelet type bleeding
What is the lifespan of platelets, neutrophils and RBCs?
Platelets= 7 days Neutrophils = 24 hrs RBCs= 120 days
What may be the only sign of neutropenia?
Fever (severely neutropenic patients cant form pus in the same way).
Which industrial chemical is an important cause of AML?
Benzene
Is AML or ALL more common and what age group does AML present in?
AML is More common than ALL.
AML is more common in adults- increasing incidence with age.
What findings aid a diagnosis of AML?
FBC- low Hb, low platelets, low granulocyte count, high blast count
Blood film- lots of blasts (high nuclear:cytoplasmic ratio)
Bone marrow histology- blasts must be >20% of nucleated cells
Flow cytometry- CD13+ and CD33+
Cytogenetics- t(15;17) prognosis = good unless you catch it too late, t(8;21), inv16 = good prognosis. Monosomy 7, abnormalities chromosome 5, chromosome 1 and complex cytogenetics = poor prognosis
What is the treatment for AML?
(Most recent addition in Tx is the antibody Mylotarg (Gemtuzumab ozogamicin) which is a CD33 antibody).
Combination chemotherapy- important drugs include cytarabine (aka. Cytosine arabinoside) and daunorubicin. Total of 4-6 months of Tx, Tx induces profound bone marrow suppression and pancytopenia so need supportive care incl: transfusion of RBCs and platelets, antiseptic mouthwashes, clean diet, oral prophylactic anti-fungal agents and quinolones.
What factors may affect prognosis in AML?
Better prognosis if <60 years and favourable cytogenetics.
FLT3-negative, NPM1 positive >60% survival
What are the clinical signs of ALL?
Similar to AML (low Hb, low platelets, high blast cells), but more frequently: lymphadenopathy, hepatosplenomegaly and CNS involvements. Commonly causes severe bone pain, sweats and weight loss.
What findings aid a diagnosis of ALL?
As for AML.
Lumbar puncture is important to determine if there is evidence of CNS disease (usually done when peripheral blasts cleared).
Flow cytometry: blasts of B cell (80%) which are CD10, CD19 and CD22 positiv or T cell lineage (20%)
Cytogenetics: Philadelphia chromosome t(9;22) seen in 20-25% of adults.
What is the treatment for ALL?
Chemotherapy with complex combinations of cytotoxic drugs e.g steroids, vincristine, daunorubicin, asparaginase (4 drug induction). Different drugs for second phase of induction.
What is meant by the term ‘minimal residual disease’?
MRD is the name given to small numbers of leukaemic cells that remain in the patient during remission. These cells can cause relapse. Therefore the less MRD a patient has, the fewer leukaemia cells they have and hence the deeper the remission and the better the prognosis.
The multi drug treatment in ALL is in 3 phases- what are these?
Induction phase- 3 months’ intense chemotherapy to induce remission
Consolidation phase- 4 months’ intense chemotherapy to consolidate the remission
Maintenance phase- 2 years less intense chemotherapy to maintain remission
What techniques are used to try and detect MRD in a patient in remission?
- Microscopy of a blood film
- FISH
- Immunophenotyping
- PCR
These go up in sensitivity (able to detect lower number of cells present)
What is complete remission (in the context of ALL lecture)
When the MRD gets so low that even the most sensitive PCR testing can’t pick up any cancer cells (hence they are MRD negative). This doesn’t mean the person doesn’t have ANY cells left, they may have <5% left but we can’t detect them
What targeted therapies are emerging for the future treatment of leukaemia?
CAR-T cells (chimeric antigen receptor T cells)- this is when the T cells are removed from a patient and modified so that they express receptors specific to the patient’s particular cancer, which can then recognise and kill the cancer cells are reintroduced into the patient. There are also some novel antibody therapies.
How does a bone marrow transplant work?
- You give very high dose (3-10x standard chemotherapy) to kill all of the patient’s bone marrow cells
- You then give the patient an injection of bone marrow stem cells
- The stem cells migrate to the bone marrow and set up camp.
- They proliferate, giving the patient a new bone marrow and hence a new immune system
- This new immune system is able to kill any remaining leukaemic cells that might have survived the initial chemo because it recognises the cancer as non-self (a graft versus leukaemia effect).
What is the mortality rate associated with bone marrow transplants and why is it high?
20% mortality, due to neutropenic sepsis and graft versus host disease
What are the long-term consequences of bone marrow transplant?
- Infertility- the high dose chemotherapy destroys the gonads
- Secondary cancers- the high dose chemotherapy causes a second cancer elsewhere later on in life (1% at 10 years and 10% at 20 years).
Where can bone marrow transplant cells come from?
Other people- allogenic transplant.
The patient themselves - autologous: before the high dose chemo you remove some healthy bone marrow cells from the patient, you freeze them, you inject them back into the patient once you’ve wiped out their bone marrow with the high dose chemotherapy. You then hope the healthy bone marrow cells repopulate the bone marrow to rescue it.
What is the definition of anaemia?
Anaemia is a condition in which the number of red blood cells (and consequently their oxygen carrying capacity) is insufficient to meet the body’s physiologic need.
How do the following factors influence haemoglobin concentration: age, gender, altitude, smoking and pregnancy.
Age: Hb concentrations fall slightly in the older populations. Neonates tend to have a high Hb when compared to the adult reference range which then falls off and during infancy they usually have a lower Hb which rises again throughout childhood until they reach adult levels.
Gender: men have a higher Hb concentration than women due to hormones.
Altitudes: higher altitudes = higher Hb concentration (due to sensing of the relative hypoxia)
Smoking- smokers have a slightly higher Hb concentration (increased Hb to account for the CO which binds some of the Hb up)
Pregnancy: in the 2nd and 3rd trimesters Hb concentration starts to fall (total number of RBCs increases but plasma volume increases to a greater extent, so the actual concentration of Hb actually decreases).
What is the structure of Hb?
A tetramer of globin monomers and a haem ring. Different globing have different oxygen carrying properties, which globins make up the Hb depends on the stage of life. Foetal Hb: 2 alpha and 2 gamma. Adult Hb= 2 alpha and 2 beta.
What is HbA2?
A type of adult haemoglobin which is present in very small amounts compared to HbA. It is composed of 2 alpha and 2 delta globulin subunits.
What factors shift the oxygen dissociation curve to the right (and hence causing O2 to be off-loaded)?
An increase in temperature
An increase in CO2 concentration
Decrease in pH
Presence of DPG
What other things can affect the oxygen carrying capacity of Hb?
Binding of CO = carboxyhaemoglobin (prevents carriage of O2)
Methaemoglobin= when the iron is in the Fe3+ state not the Fe2+ state (prevents carriage of O2)
Carbaminohaemoglobin- form of Hb complexed with CO2- accounts for ~10% of CO2 carriage.
Sulphhaemoglobin- O2 cannot be delivered or carried. May be produced by the action of sulphur containing drugs and cannot be converted back to Hb.
What are some of the general features of anaemia?
Pallor Peripheral oedema Tachycardia Flow murmur (when blood flows more rapidly than normal through the heart) Palpitations Shortness of breath (esp. on exertion) Confusion (esp. in the elderly)
What is the most useful parameter when considering the cause of anaemia? Tell me briefly about it
Mean cell volume (MCV). It is the mean size of the RBCs and is the normal range is the same in men and women.
What are the causes of a microcytic anaemia?
Iron deficiency, thalassemia, anaemia of chronic disease
What are the causes of a normocytic anaemia?
Acute blood loss, haemolysis, anaemia of chronic disease, bone marrow infiltration, combined haematinic deficiency
What are the causes of a macrocytic anaemia?
B12/folate deficiency Haemolysis Hypothyroidism Liver disease Alcohol excess Myelodysplasia
What are some of the causes of iron deficiency?
Dietary (80% from meat, 20% from vegetables)
Physiological (infancy, adolescence, pregnancy)- describes a state where requirements of iron for growth are increased but these requirements are not being met through the diet.
Blood loss (note: chronic blood loss, not acute where you get a normocytic anaemia)
Malabsorption (e.g. coeliac disease)
Iron deficiency anaemia- what are the clinical features if it is severe?
Angular stomatitis (sores around the mouth)
Sore mouth
Koilonychia (spoon shaped nails)
Pharyngeal and oesophageal webs (rarely)
What are the laboratory features of iron deficiency anaemia?
Microcytic hypochromic anaemia.
Hypochromic means the cells don’t stain so brightly.
Low serum ferritin (beware as it is an acute phase protein, so in patients with inflammation/infective process, their ferritin levels will be bumped up which can mask iron deficiency as a cause of anaemia). Ferritin is the main storage complex of iron.
Low serum iron
Absent iron stores in the bone marrow (but wouldn’t tend to look at this)
Elevated TIBC (total iron binding capacity) and serum transferrin saturation
What characteristic feature might you see on the blood film of someone who is iron deficient?
Microcytic hypochromic anaemia. Some cells may also appear elongated/ oblong- these are called ‘pencil cells’.
What are the principles behind further investigations in iron deficient patients?
If think it has a physiological cause- treat with oral iron (until the period of physiological need has settled down)
If pre-menopausal female and thought likely to be due to periods (no GI problems) also treat with oral iron. However, if any worrying GI signs/symptoms or the woman is not having periods for whatever reason (e.g. OCP) then they should be investigated more throughly (e.g. colonoscopy/OGD). Similarly, males and post-menopausal women should be investigated.
What is meant by the term ‘anaemia of chronic disease’?
Depression of erythropoiesis of multifactorial aetiology seen as a secondary manifestation in a wide variety of disorders (usually chronic inflammatory process). More commonly a normocytic normochromic anaemia but can be microcytic hypochromic. Serum ferritin may be normal or increased (increased esp. if inflammatory process).
What things start to go wrong in anaemia of chronic disease?
Iron sequestration in macrophages and failure of transport of iron from reticular endothelial system to developing cells.
Slightly shortened red cell survival (their circulating half-life is shorter).
What is the treatment of anaemia of chronic disease?
Correction of underlying cause. Erythropoietin (+iron)
What type of anaemia do you see in vitamin B12 deficiency?
Macrocytic megaloblatic anaemia. (Megaloblastic means that you can identify an abnormality in the developing RBCs in the bone marrow- it results from inhibition of DNA synthesis during red blood cell production).
How is vitamin B12 absorbed?
It combines with intrinsic factor (IF) secreted by gastric parietal cells and is absorbed in the terminal ileum.
What are the causes of vitamin B12 deficiency?
Dietary: vegan is
Intrinsic factor deficiency: pernicious anaemia, gastrectomy, congenital
Intestinal malabsorption: diseases of the terminal ileum e.g. Crohn’s disease, blind loops and small bowel diverticula.
What are the clinical features of vitamin B12 deficiency?
Anaemia, jaundice (because the RBCs that are produced are broken down more readily in the circulation), glossitis (sore tongue), neurological deficit (this can even be seen in the absence of anaemia).
What are the laboratory features of vitamin B12 deficiency?
Anaemia, neutropenia, thrombocytopenia (because vitamin B12 is required for DNA synthesis and production of many cell types). On a blood film vitamin B12 deficiency can actually look like a haematological malignancy because you see a pancytopenia and the cells look a bit abnormal. Low serum vitamin B12. Antibodies against parietal cells or IF. Megaloblastic change in bone marrow. Features of haemolysis.
What type of anaemia results from folate deficiency?
Macrocytic Megaloblastic anaemia
Where in the body is folate absorbed?
The jejunum
What are the causes of folic acid deficiency?
Dietary- common in elderly, poor diet related to alcohol misuse
Increased utilisation- pregnancy, malignancy, haematological disorders with rapid cell turnover
Malabsorption e.g. coeliac disease
Drugs e.g. anticonvulsants
Excessive loss e.g. renal dialysis
What are the clinical features of folic acid deficiency?
Similar to vitamin B12 deficiency but neurological problems do not occur.
What is the treatment for B12/folate deficiency?
Address underlying cause. If the problem (with regards to vit B12) is that you don’t have enough IF, then giving oral vit B12 won’t help because the patient still wont be able to absorb it, so in these cases vit B12 is given by IM injection. Vitamin B12 replacement as IM infection most common -3 times per week for 2 weeks then maintenance phase. Oral folic acid replacement (even in malabsorptive conditions if you give a high enough dose then it will start to be absorbed more readily).
What do you need to be careful about when treating vitamin B12 and folate deficiency and how do you avoid the potentially fatal complication?
Risk of subacute combined degeneration of the cord (with permanent neurological sequence) if folic acid is replaced in the absence of vitamin B12- so always remember to replace vitamin B12 before folate in people who are deficient in both vitamin B12 and folate (or at least do them at the same time).
What is meant by combined haematinic deficiency?
Remember that MCV is a MEAN value. Therefore a combination of large and small red cells can produce an MCV within the normal range (e.g. in a patient with a really poor diet who you suspect is iron, folate and vitamin B12 deficient despite a normal MCV).
What is haemolysis?
Reduced red cell survival (normal life span 120 days) - the problem isn’t with production. RBC breakdown can be: intravascular (within the vessels releasing free Hb) or extravascular (by the reticulo-endothelial system) - predominantly the spleen. Erythroid expansion and increased production (up to 7 fold) by the bone marrow may partly compensate.
What are the inherited causes of haemolytic anaemia?
Membrane: hereditary spherocytosis - autosomal dominant
Enzymes: G6PD deficiency - x linked recessive. And pyruvate kinase deficiency - autosomal recessive
Haemoglobin: sickle cell anaemia, thalassaemia (both autosomal recessive)
What are the acquired causes of haemolytic anaemia?
Immune: autoimmune (can be primary or secondary to lymphoproliferative autoimmune disorders, infections, drugs) OR alloimmune i.e. the red cells and the immune system don’t match (e.g. haemolytic disease of the newborn or incompatible blood transfusion).
Infections: many mechanisms
Drugs and chemicals: many mechanisms
Mechanical: (where red cells are sliced up): MAHA
Other rare types: e.g. paroxysmal nocturnal haemoglobinuria
What does MAHA stand for?
Microangiopathic haemolytic anaemia (the red cells are sliced up in the very small blood vessels/ microvasculature)- so it’s a type of intravascular haemolysis, usually in sick patients)
What are the clinical features of haemolysis?
Anaemia (symptoms and signs associated with anaemia)
Jaundice (unconjugated bilirubin i.e. pre-hepatic)
Splenomegaly (if extravascular haemolysis and the spleen is busy breaking down RBCs)
Skeletal abnormalities (congenital forms of haemolysis when the bone marrow is trying to compensate)
Gallstones (pigment stones (bilirubin) suggest chronic haemolysis)
Haemoglobinuria (denotes intravascular haemolysis)
What are the features for a laboratory diagnosis of haemolysis?
Increased RBC production: reticulocytosis, polychromasia on blood film (reticulocytes are slightly blue tinged).
Increased RBC destruction: unconjugated hyperbilirubinaemia, increased LDH (non-specific, as any type of increased cell turnover/ breakdown will give you an increased LDH). Absent haptoglobins (they bind and clear free Hb so may be reduced). Intravascular: haemoglobinaemia, haemoglobinuria, haemosiderinuria
What are the laboratory investigations you can conduct to determine the cause of haemolysis (once you’ve established its haemolysis)?
Blood film is the most useful investigation (further investigations are directed by this and the clinical features)
Coombs test is used to detect immune coating on RBC by Ig and complement - is positive suggests immune cause, but does not differentiate between autoimmune or alloimmune
Tell me about spherocytes
Each time the RBC goes through the spleen, a bit more membrane is haemolysed -> volume to surface area ratio is increased (end result is a sphere). On the blood film: lose their pallor and look like small dense circles. Spherocytes may be indicative of HS (hereditary spherocytosis) or autoimmune haemolytic anaemia (history and Coombs test will help distinguish).
What does the presence of red cell fragments indicate?
MAHA (microangiopathic haemolytic anaemia).
The RBCs look like they have been chopped with a knife.
What are some of the causes of MAHA?
TTP (thrombotic thrombocytopenic purpura) HUS (haemolytic uraemic syndrome) DIC Prosthetic valve haemolysis Vascularise HELLP syndrome Malignant hypertension Metastatic adenocarcinoma
On which chromosomes are the genes that encode the globulin proteins?
Chromosomes 11 and 16. Note: proteins produced from both chromosomes are needed to make normal Hb (usually 2 alpha globins combine with 2 non-alpha globins).
What are haemoglobinopathies?
Inherited genetic defects of globin. Sickling disorders and thalassaemias are the most clinically important (both are autosomal recessive and carriers are asymptomatic). Note that mutations of the alpha globin genes affect both foetal and adult life. Beta globin mutations only manifest after birth when HbA replaces HbF.
What is thalassemia?
Reduced or absent synthesis of globin. Beta thalassaemia (beta globin). Alpha thalassaemia (alpha globin).
What is sickle cell anaemia in brief terms?
Altered beta globin protein structure/ function
Where in the world are thalassaemias more frequently found?
In the Mediterranean, Africa, western and Southeast Asia, India and Burma
What are the various clinical types of beta thalassaemia?
Beta thalassaemia trait (carrier status)- genotype beta0, beta. Asymptomatic, normal life span.
Beta thalassaemia intermedia- variable genotype, phenotype and life span.
Beta thalassaemia major- genotype beta0, beta0. No beta globin and no HbA. Early death if untreated (because it’s the beta gene, newborn babies aren’t symptomatic but they are very soon in the months after birth).
What is the pathophysiology of beta thalassaemia major?
Complete absence of HbA (as no beta globin). Excess alpha chains accumulate and damage red blood cells. Ineffective erythopoiesis. Excessive RBC destruction (intramedullary and extramedullary). Iron overload. Extra-medullary haemtopoiesis.
