Haematology Flashcards
Describe the importance of the bone marrow microenvironment in haemopoiesis
The bone marrow microenvironment (stroma) supports developing haematopoietic stem cells
It provides a rich environment for growth and development of stem cells
Stromal cells are supported by an extracellular matrix
Stromal cells include; Macrophages, Fibroblasts, Endothelial Cells, Fat Cells, Reticulum Cells
Describe the major myeloproliferative disorders
Clonal blood disorder characterised by over effective haemopoiesis
JAK2 mutation is highly prevalent
Too many platelets = Essential Thrombocytosis
Too many RBCs = Polycythaemia Rubra Vera
Too much fibrous tissue = Myelofibrosis
- ET & PRV
- Good outcome
- Risk of vascular events (managed with aspirin)
- Managed by cytoreduction (hydroxycarbamide, venesection or interferon)
- 5-10% risk of progression to AML
- 10% progress to myelofibrosis
- MF
- Splenomegaly + Systemic Symptoms
- Blood counts may be high or low
- Incurable other than with SCT
- New drug class - JAK2 inhibitors
Describe myelodysplastic syndrome
Clonal blood disorder characterised by failure of effective haemopoiesis (low blood count)
More common in the elderly
Dysplastic blood and marrow appearance
Approx. 25% rate of progression to AML
(Blast cell % cut off for MDS vs AML is 20%)
Symptoms characterised by consequences of marrow failure
Incurable other than with SCT for those <65yrs
Consider supportive care and drug therapy (e.g. azacitidine)
State the requirements for normal RBC production
Erythropoietin (Drive for Erythropoiesis)
Genes (Recipe for Erythropoiesis)
Iron, B12, Folate and Minerals (Ingredients for Erythropoiesis)
Functioning Bone Marrow
No Increased Loss or Destruction of RBCs
Describe the physiology of B12 metabolism
Essential for DNA synthesis and nuclear maturation
Required for all dividing cells
B12 (Cobalamin) necessary for methionine production and methylmalonyl-CoA isomerisation
Found in meats (esp. liver and kidney)
Require 1ug/day
Absorbed with Intrinsic Factor in the ileum
Stores in the body for 3-4 years
Describe the physiology of Folate metabolism
Essential for DNA synthesis and nuclear maturation
Required for all dividing cells
Found in green veg (but destroyed by cooking)
Absorbed in the small intestine (no carrier molecule required)
Only a few days store in the body but quickly used up if there is increased demand (i.e. increased cell turnover)
Describe the effects of B12/Folate deficiency
Affects all tissues with rapidly growing, DNA synthesising cells (bone marrow, epithelia etc.)
Blood (B12 and Folate) - Megaloblastic Anaemia
Neurological (B12) - Bilateral Peripheral Neuropathy, Demyelination of the Posterior and Pyramidal Tracts of the Spinal Cord
Growing Foetus (Folate) - Neural Tube Defects in first 12 Weeks
State causes of B12 and Folate deficiency
B12 - Dietary, Pernicious Anaemia, Gastrectomy, Achlorhydria, Crohn’s, Ileal Resection
Folate - Dietary, Coeliac, Severe Crohn’s, Haemolysis, Severe Skin Disorders, Pregnancy
Define haemoglobinopathies
‘a group of inherited conditions characterised by a relative lack of normal globin chains due to absent genes (thalassaemias) or abnormal globin chains (e.g. sickle cell disease)’
Describe Alpha-Thalassaemia
Relative lack of alpha globin chains
Alpha globin chains are duplicated on each chromosome for a total of 4 genes
Prevalent in Meditteranean countries, Africa, South East Asia and the Indian subcontinent
If missing 4 Genes - Incompatible with Life
If Missing 3 Genes - HbH Disease (significant anaemia and abnormally shaped RBCs)
If Missing 1/2 Genes - Alpha Thalassaemia Trait (mild anaemia, microcytosis, reduced MCV and MCH but increased RBC count)
Describe Beta-Thalassaemia
Deficiency in beta globin genes (should normally two)
Prevalent amongst Greek Cypriots, Turks, Asians and Africans
Beta Thalassaemia Major - Missing Both Genes - Autosomal Recessive - Severe anaemia due to ineffective erythropoiesis and haemolysis renders patient transfusion dependent from early life with iron overload being the major problem
Thalassaemia Intermedia
Beta Thalassaemia Trait - May be a mild microcytic anaemia, is often confused for IDA
Describe Sickle Cell Disease
Arises due to abnormal HbS which occurs following a single amino acid substitution in the beta-globin gene
RBCs undergo sickling
Results in reduced RBC survival due to haemolysis and vaso-occlusive crises leading to tissue hypoxia and infarction
Complications include Stroke, Moya Moya, Acute Chest Syndrome, Retinopathy, Osteonecrosis
Crisis Prevention - Hydration, Analgesia, Vaccination, Antibiotics and Folic Acid
Cris Management - Oxygen, Fluids, Analgesia, Antibiotics, Transfusion
Can be cured with Bone Marrow Transplantation
Describe the Direct and Indirect Coombs Test
The Coombs test detects autoantibodies against antigens on the RBC membrane
The direct test detects antibodies on the RBC surface and is positive in Haemolytic Disease of the Newborn and Acquired Immunohaemolytic Anaemia
The indirect test detects antibodies in the plasma and is used in prenatal screening of Rh antibodies
Describe an approach to the investigation of a patient with anaemia
- Is it new?
- Congenital or Acquired?
- History
- Blood Loss
- Diet
- Chronic Disease
- Family History
- Medication
- Examination
- Angular Stomatitis
- Splenomegaly
- Lymphadenopathy
- Abdominal Masses
- Haematology
- Size of RBCs
- Are WBCs/Platelets affected?
- Is marrow able to mount a reticulocyte response?
- What are the haematinic results?
- What does the blood film look like?
Define Lymphoma and describe a basic classification system
‘a group of malignancies of lymphoid tissue with accumulation of B/T-Lymphocytes’
Broadly divided into Hodgkin and Non-Hodgkin Lymphomas
Describe the pathology of Hodgkin Lymphoma
The malignant cells (Reed-Sternberg and Hodgkin’s cells) comprise a minority of the tumour, with the remainder comprised of lymphocytes, granulocytes, fibroblasts and plasma cells
Reed-Sternberg cells are bi/multi-nucleated giant cells of B-Lymphocyte origin
Up to 40% of HL cases are associated with EBV
Describe the clinical presentation of Hodgkin Lymphoma
Bimodal Age Incidence (20s-30s and >50s)
Painless Lymphadenopathy (Cervical or CXR Mass)
Spread from one nodal group to adjacent
Later there may be haematogenous spread to liver or lungs
May have B symptoms (fever, drenching night sweats or weight loss)
Managed by Chemo and Radiotherapy
Describe the clinical presentation of high-grade Non-Hodgkin’s Lymphomas such as Diffuse Large B-Cell Lymphomas
Most common subtype of NHL
Increasing incidence with age
Aggressive
Often presents with localised or generalised painless lymphadenopathy
40% present extra-nodally with abdominal pain, anaemia, CNS disease or on the skin
May also present with Pyrexia of Unknown Origin
Managed by R-CHOP Chemotherapy +/- Radiotherapy
Describe the pathology of low-grade/indolent Non-Hodgkin’s Lymphomas such as Follicular Lymphoma
B-Cell Lymphoma
90% of follicular lymphomas are characterised by the t(14;19) translocation where the BCL2 gene on chromosome 18 is moved to the immunoglobulin heavy chain
This leads to excessive expression of BCL2, an oncogene known to inhibit apoptosis
it is likely that further change (e.g. activation of a proto-oncogene or an antigenic stimulus) produces the clonal malignancy
Describe the clinical presentation of low-grade/indolent Non-Hodgkin’s Lymphomas such as Follicular Lymphoma
Increasing incidence with age
Median presentation between 60-65 years
Often presents with late-stage disease due to its indolent course
Local disease may be managed with radiotherapy but most cases require a rituximab-containing regime (e.g. R-CVP or R-CHOP)
Average survival of 15-20 years
Responsive to treatment but tendency to relapse or transform to DLBCL
Describe the staging of Lymphoma
Ann-Arbor Staging System
I - Single Lymph Node Group
II - More than one LN group on the SAME side of the diaphragm
III - LN groups on BOTH sides of the diaphragm
IV - Extranodal involvement (e.g. liver, bone marrow)
A or B is added to signify absence or presence of B symptoms (fever, night sweats, weight loss)
Early Stage = 1 or 2A
Advanced Stage = 2B or 3 or 4
Describe the diagnosis of Lymphoma
Excision or Core Biopsy of Lymph Node, Other Tissue or Bone Marrow
CT Neck, Chest, Abdomen and Pelvis
PET-CT
Define Multiple Myeloma
‘a clonal malignancy characterised by uncontrolled proliferation of plasma cells in the bone marrow and production of monoclonal immunoglobulin’
Describe the pathophysiology of Multiple Myeloma
MM is preceded by a clinical syndrome known as Monoclonal Gammopathy of Undetermined Significance
Plasma cells in the bone marrow secrete paraprotein (monoclonal immunoglobulin or immunoglobulin fragments)
Most produce IgG or IgA or light chains only
Occasionally myelomas may be non-secretory
Myeloma Triad = Increased Plasma Cells in the Bone Marrow + Clonal Immunoglobulin/Paraprotein + Lytic Bone Lesions
Describe the clinical presentation of Multiple Myeloma
Back Pain
Rib Pain
Pathological Fractures
Vertebral Collapse
Anaemia
Thrombocytopenia
Frequent Infection
Hypercalcaemia
Renal Failure
Describe the main differences between Hodgkin’s (HL) and Non-Hodgkin’s (NHL) Lymphoma
NHL is a monoclonal proliferation of B/T-Lymphocytes and HL is a lymph malignancy of proliferating germinal centres
EBV is associated with both
HL has a bimodal age distribution
HL is characterised by presence of Reed-Sternberg Cells
Both present with painless lymphadenopathy and possibly B symptoms and HL may also present with pruritis
Contiguous LN spread in HL, Non-Contiguous LN spread in NHL
Radiation and Chemotherapy for both
State techniques used to diagnose Lymphoma
Morphology
Immunohistochemistry
Flow Cytometry
Karyotyping
Fluorescence in situ Hybridisation
PCR Clonality Assays
Gene Sequencing/Array Based Technologies
Describe lymphocyte development
B-Cells are produced in bone marrow from a committed stem cell progenitor
Mature B-Cells circulate in peripheral blood and populate lymphoid and other organs
T-Cells originate in bone marrow from committed stem cell progenitor
Precursor T-Cells migrate to thymus where they develop into mature T-Cells
Mature T-Cells circulate in peripheral blood and populate lymphoid and other organs
Describe the physiological processes involved in the coagulation system
- Blood Vessel Damage
- Endothelial Disruption
- Exposure of Tissue Factor and Collagen
- Primary Haemostasis
- Recruitment of Platelets
- Secondary Haemostasis
- Activation of Coagulation Factors
- Cascade:
- Initiation - Extrinsic Pathway
- Propagation - Intrinsic Pathway
- Thrombin Generation
- Fibrin Production (The Clot)
- Each step in the cascade requires phospholipids from the platelet surface and calcium
State the laboratory tests used to assess the coagulation system
- Assessment of Primary Haemostasis
- In Vivo - Bleeding Time
- Ex Vivo - FBC, Platelet Count, Platelet Function
- Assessment of Secondary Haemostasis
- Prothrombin Time (PT)
- Activated Partial Thromboplastin Time (APTT)
- Thrombin Clotting Time (TCT)
- Individual Coagulation Factor Assays
Describe the use of Prothrombin Time (PT) to assess the coagulation system
Simulates activation via the extrinsic pathway
Add patient’s plasma and thromboplastin, warm to 37C, add calcium and time taken to form clot
Normal range is 10-13 seconds
Ratio is the patient’s PT/average of 20 normal PTs (normal ratio is 1 - 1.2)
PT depends on factors in the extrinsic and common pathways (Factors VII, X, V, II and Fibrinogen)
Describe the use of International Normalised Ratio (INR) to assess the coagulation system
The standardised form of prothrombin time
Used in the monitoring of oral coumarins such as Warfarin
A patient’s INR is identical in any laboratory
Patient’s PT/Average of 20 Normal PTs
Result factored by the International Sensitivity Index (ISI)
Every thromboplastin preparation has its own ISI
Describe the use of Activated Partial Thromboplastin Time (APTT) to assess the coagulation system
Stimulates activation via the intrinsic pathway
Add the patient’s plasma, contact factor and phospholipid
Warm to 37C and add calcium and time the taken to form a clot
Normal range is 26-38 seconds
Ratio of Patient/Average of 20 Normals
APTT depends on factors in the intrinsic and common pathways (Factors VIII, IX, XI, XII, X, V, II and Fibrinogen)
Describe the use of Thrombin Clotting Time (TCT) to assess the coagulation system
Measures conversion of fibrinogen to fibrin clot
At 37C, add the patient’s plasma and bovine thrombin
Less calcium or phospholipid-dependent
Measure the time taken to clot
Normal range is 10-16 seconds
Depends on how much fibrinogen is present in the plasma and how well it functions
Will also be prolonged by inhibitors of thrombin (heparin, dabigatran), FDPs or inhibitors of fibrin polymerisation (paraprotein)
State and briefly describe the three classes of anti-thrombotics
Anti-Coagulants (inhibit one or several components of the coagulation cascade)
Fibrinolytic Agents (enhance lysis of the fibrin clot)
Anti-Platelet (inhibit platelet activation or aggregation)
Describe some of the acquired disorders of the coagulation system
- Disseminated Intravascular Coagulation
- Acquired, consumptive process with activation of the coagulation cascade (resulting in microthrombi) and subsequent exhaustion of the coagulation cascade (resulting in bleeding)
- Caused by sepsis, malignancy, massive haemorrhage, severe trauma or complications in pregnancy
- Treat the underlying cause and give FFP +/- platelets if bleeding or at high risk
- Warfarin-Induced Bleeding
- If INR is too high, stop warfarin or reduce dose, give Vitamin K or give coagulation factors
- Coagulopathy in Liver Disease
- Poor coagulation factor synthesis due to liver damage
Describe some of the inherited disorders of the coagulation system
- Haemophilia A
- Classical Haemophilia
- Factor VIII Deficiency
- Prolonged APTT
- X-Linked Inheritance
- Replacement with Recombinant Produced Factor Concentrate
- Von Willebrand Disease
- VW Factor facilitates platelet adhesion and aggregation in primary haemostasis
- Binds Factor VIII and prolongs its half-life in the plasma
- Thrombophilia
- Deficiencies of natural anticoagulants such as antithrombin, Protein C or Protein S
- May be due to specific gene mutations such as Factor V Leiden (resistance to APC) or the prothrombin gene (which results in increased prothrombin)
