Haemopoiesis Matthew Hazell Consultant Clinical Scientist Trainee
Learning objectives Describe haemopoiesis and the development of blood cells from stem cells to mature cells Explain the roles of the different blood cells Indicate the normal ranges for full blood count and explain what each measurement means Recognise how to detect abnormal results and interpret possible causes Explain what further tests should be performed and could help diagnose the cause of abnormal results Recognise the different types of anaemia and review case studies
Describe Haematopoiesis and the development of blood cells from stem cells to mature cells Haematopoiesis: The Formation and development of blood cells Fetus Yolk Sac Liver and Spleen Child Most Bone marrow space (Axial skeleton and Distal Long bones) Adult Axial Skeleton
Fetal haemopoiesis Conception 6 weeks Yolk Sac - Blood islands (mainly produce erythrocytes) 6 weeks 6 months Fetal liver and spleen 6 months childhood Bone marrow of nearly all bones
Adult Bone Marrow Axial (Central) Skeleton 30% of active marrow sites are haemopoietic (red marrow) Remainder = yellow marrow (fat cells) Chronic haemolytic anaemia Increased cellularity in bone marrow Myeloproliferative disorders liver and spleen active again Diagnostics Iliac Crest (Sternum sometimes used) Gordon-Smith, T., (2009). Haemopoiesis the formation of blood cells. Medicine 37(3), pp.129-132.
What is responsible?
Differentiation Myeloid Lymphoid
Regulation of haematopoiesis
Haematopoietic Growth Factors
Normal Haematopoiesis Defective Haematopoiesis per day 200 billion red cell, 100 billion white cells, 100 billion platelets Can increase by a factor of 10 Pancytopenia Deficiency of all three cellular components of the blood Red cells - anaemia white cells - leukopenia platelets - thrombocytopenia Acquired conditions Auto immune aplastic anaemia Leukaemia Bone marrow infiltration Inherited conditions Fanconi Anaemia Dyskeratosis Congenita Blackfan Diamond anaemia Shwachman Diamond syndrome Toxins Alcohol Lead
Roles of blood cells
Erythrocytes (Red Blood Cells) Biconcave shape No nucleus or internal organelles Larger surface area Flexible 120 day lifespan Size = 7.2µM Normal concentration = 3.9-6.5x10 12 /L Contain Haemoglobin (97% = 250 million per cell) Haemoglobin = 8 components 4 haems + 4 globin 2(αβ) Binds oxygen (lungs) Binds carbon dioxide (tissues)
Platelets Disc shaped No nucleus Granule containing cell fragments Formed by megakaryocytes 2-3µM 7-10 day lifespan 1/3 of platelets sequestered in spleen Function Coagulation Adhere Change shape (sphere) Cytoplasmic projections Promotes platelet platelet interaction Fibrin Clot
Neutrophils (Polymorphonuclear leucocytes) Multi-lobed nuclei (2-5 lobes) Women drumstick appendage that contains inactive X chromosome Few mitochondrion large stores of glycogen Size 9-15µM Circulate for 10hours Migrate to tissues (chemotaxis) Survive 1-3 days in tissue Function Primary cells to reach inflammation Arsenal Phagocytosis Release of hydrolytic enzymes
Eosinophils Bi lobed sausage shaped nuclei Limited organelles (central Golgi, rough ER, mitochondrion) Large (1-1.5µM) ovoid, specific granules and azurophilic granules (stain with Romanowsky stain) Size = 12-17µM Found in tissues < 1hour in blood Function Seen in allergic/malignant disease Combat parasites Arsenal Phagocytose antibody/antigen complexes
Basophils Bi lobed S-shaped nucleus Specific granules (0.5µM) and azurophilic granules Large membrane bound structures give roughened appearance Granules contents = heparin, histamine, chemotactic factors, peroxidase Mature over 2-7 days in bone marrow Lifespan = 14 days Function Similar to mast cells (different cell lineage) Arsenal Interact with IgE, cause local inflammatory response (Asthma/anaphylaxis (type 1 hypersensitivity)
Monocytes Large kidney shaped nuclei (moth eaten appearance = nucleoli) Cytoplasm contains lysosomes/vacuole spaces (ground glass appearance Largest blood cell in circulation Size = 25µM Present in blood for few days then migrates to tissues Matures into macrophage Macrophage lifespan = several months years Function Reticuloendothelial system Destroys dead/defunct cells Presents to lymphocytes to initiate adaptive immune response Arsenal Phagocytosis Release of pro inflammatory cytokines
Lymphocytes (B Cells, T Cells, Natural Killer Cells) (Antibody mediated immunity) (Cell mediated immunity) Round shape (can change shape) Round densely stained acentric nuclei Sparse cytoplasm unless activated Move between tissues, lymph and blood Lifespan = dependant on interaction with antigen Memory cells can survive for decades Function Kill foreign and virally infected cells Arsenal Produce antibodies Complement Reactive oxygen species
Full Blood Count FBCs, like all lab results, are like photos They are only valid for the time at which they were taken GIGO principle (Garbage In, Garbage Out) If the sample was not taken properly and handled correctly, the results may be inaccurate If a result looks strange and does not fit the way the patient looks, check again! (presuming it is not urgent) And tell the lab you think it might be wrong
Abnormal results
Anaemia according to WHO
Classification of anaemia By Underlying Cause Decreased Production Increased Destruction Blood Loss Haemorrhage situation? If not look at the size of the red cells (MCV)
Normal distribution MCV average RBC volume (Mean corpuscular volume) RDW range of variation of RBC volume (Red cell distribution width)
Classification of anaemia - Morphology Microcytic, hypochromic MCV Decreased Normocytic, normochromic Macrocytic MCV increased
Anaemia-microcytic (small red cells) MCV < 85fl * Iron deficiency (by far the likeliest cause) Dietary Bleeding (GI, FCBP) Haemoglobinopathy (thalassaemias mainly) these people can also be iron deficient Anaemia of chronic disease Rare causes
Anaemia-macrocytic (enlarged red cells) MCV > 100fl B12 / folate deficiency Excessive alcohol intake (chronic) High red cell turnover (eg haemolysis, bleeding) Myelodysplastic Syndrome (MDS) Certain drugs (eg hydroxycarbamide, azathioprine)
Anaemia-normocytic (red cell size normal on average) MCV 85-100fl Can happen with any of the previous causes Mixed picture of low/high MCV Traditionally said to be likeliest with anaemia of chronic disease or renal anaemia
Anaemia Other (possibly) useful investigations: Ferritin, B12, folate levels U&Es, LFTs, TFTs Blood film Reticulocyte count (and haemolysis screen) Hb electrophoresis Always look for the trend is this new or old? Is it falling quickly or slowly?
Anaemia Patients may tolerate extremely low Hb levels if it has fallen slowly and they have had time to compensate Conversely, rapidly falling Hb levels can make people feel ill even at moderately low levels So history and examination / clinical picture is critical to making good decisions
Anaemia A more detailed pathway of management of types of anaemia will be presented later in the PBM talk.
Transfusion Dependent Patients These patients behave slightly differently to acute or chronic anaemia from other causes Decisions to transfuse tend to be based on a particular Hb threshold established over time by the patient and their caring team Some patients see marked benefit from transfusion, others very little
Abnormal results Reactive Infection (bacterial) Inflammation Malignant Myeloproliferative Chronic Myeloid Leukaemia Chronic Myelomonocytic Leukaemia Acute Myeloid Leukaemia Investigations Blood film CRP ESR JAK2 BCR-ABL Bone Marrow Treatment Specialist treatment based on test results
Abnormal results Failure of production Malignancy Aplastic anaemia Congenital Haematinic deficiency Destruction Chemotherapy Autoimmune Drugs Investigations Blood film Virology Autoimmune screen Abdo USS Bone Marrow Treatment G GSF
Abnormal results Lymphocytosis Reactive Infection (viral) Malignant Chronic lymphocytic leukaemia Acute lymphoblastic leukaemia Lymphoma Lymphopenia Infection (especially viral - HIV) Drugs Investigations Blood film Virology Immunophenotyping CT (if suspect lymphoma) Biopsy (lymphoma) Bone Marrow Investigations Blood film Viral Screen Treatment Anti viral medication Chemotherapy Stem cell transplantation
Abnormal results Reactive Infection Inflammation Hyposplenism Iron deficiency anaemia Primary Myeloproliferative disorder Investigations Blood Film C-reactive protein (CRP) Iron studies JAK-2 Bone marrow Treatment Cyto-reductive agents
Abnormal results Failure of production Malignancy Haematinic deficiency Liver failure Alcohol Drugs Infection Destruction Idiopathic thrombocytopenia purpura Thrombotic thrombocytopenic purpura Disseminated intrascular coagulation Investigations Blood Film Haematinics LFTs CRP Viral screen Bone marrow Treatment Change to drug regime Platelet transfusion Auto antibody reduction (steroids)
Pseudothrombocytopenia or spurious thrombocytopenia is an in-vitro sampling problem which may mislead the diagnosis towards the more critical condition of thrombocytopenia. The phenomenon occurs when the anticoagulant (EDTA) used while testing the blood sample causes clumping of platelets which mimics a low platelet count.
Further investigation Check the trend has it always been low? Revisit history and examination Investigate for underlying cause Blood film is always useful!
Case 1 A 24 year old woman is admitted to MAU after attending her GP with tiredness and having a FBC check: Hb 64g/L, MCV 62, WCC 7, Plts 500 What is the likeliest cause of her anaemia? What other blood tests should be done? What other questions should you ask her?
Case 1 You are asked to authorise a 2u red cell transfusion as she feels very tired, a bit breathless on climbing stairs, and has 3 young children to care for at home How would you respond? What are the options for treating her?
Case 2 A 78 year old man is an inpatient on the gastro ward in your hospital, with weight loss and not eating or drinking -? a possible upper GI malignancy. He has his routine FBC done one morning and Hb has dropped from 123g/L (2 days ago) to 55g/L this morning You rush to see him He says he doesn t feel well overall
Case 2 Once you have established his ABC are ok and observations are normal, what should you look at next?
Case 2 What is the likeliest cause? What should you do next?
Learning objectives Describe haemopoiesis and the development of blood cells from stem cells to mature cells Explain the roles of the different blood cells Indicate the normal ranges for full blood count and explain what each measurement means Recognise how to detect abnormal results and interpret possible causes Explain what further tests should be performed and could help diagnose the cause of abnormal results Recognise the different types of anaemia and review case studies