Haematology Flashcards
What are the key steps controlling Hb production
- Renal juxtaglomerular apparatus senses the level of oxygenation of the blood
- In responses to hypoxia, EPO is released from the kidney
- This stimulates erythropoiesis, increasing RBC numbers and blood oxygenation
Red cell formation can be impaired by insufficient or ineffectie erythropoiesis. What is the meaning of each of these terms? How may the be distinguished?
- Insufficient erythropoiesis: reduced quantity of erythropoietic tissue e.g. due to marrow failure
- Ineffective erythropoiesis: a high death rate among red cell precursors within the bone marrow e.g. due to nurtitional deficiency
The reticulocyte count may be used to distinguish ineffective or insufficient erythropoiesis - reticulocytes will be reduced in insufficient erythropoiesis, but raised or normal in ineffective erythropoiesis
Anaemias are classified by mean corposcular volume (MCV) and mean cell haemoglobin (MCH). What are these classifications?
- Low MCV and Low MCH - Microcytic anaemia
- High MCV - Macrocytic anaemia
- Normal MCV and MCH - Normochromic normocytic anaemia
What are the two causes of microcytic anaemia?
- Iron deficiency: This in itself has many causes
- Thalassemia trait: formation of abnormal Hb molecules leads to excess destruction of RBC and resulting anaemia
What are the 4 main causes of Fe2+ deficiency leading to a microcytic anaemia?
- Poor intake: commonest in infants, preschool children, women of child bearing age and the elderly
- Bleeding: GI malignancies, menorrhagia
- Malabsorption - coeliac disease (iron absorbed in upper GI tract - lower part of duodenum or upper part of jejunum)
- Pregnancy
What is normocytic anaemia? What are the causes?
- The anaemia of chronic disease, associated with a MCV within normal range, and normal MCH (normochromic)
- Caused by chronic infection, inflammation, malignancy, renal failure
Both microcytic and normocytic anaemia are associated with reduced serum iron. What would the findings be in terms of transferrin and ferritin to differentiate iron deficient anaemia from the anaemia of chronic disease
What is myelodysplasia (myelodysplastic syndrome)? Who does it typically present in?
Myelodysplasia is a dysplastic disorder of bone marrow stem cells, in which a number of hetrogenous changes are acquired, leading to a sequential purturbation of the haematopoietic cell fate.
Median age of onset is 60-75 - rarely presents in children. Typically there is no acute history.
How will patients with myelodysplasia present? Describe the typical laboratory features.
Typically there will be a reduction in atleast two myeloid cell lines, including:
- A macrocytic anaemia, with dysplastic appearance of red cells (fatigue, etc)
- Thrombocytopaenia, with dysplastic megakaryocytes and variation in platelet size (purpura)
- Neutropenia, often with hypogranular and dysplastic neutrophils (mouth ulceration, infection)
Blood film will be clasically described as “hypogranular neutrophils with a dysplastic appearance.”
How does the pathological change in MDS (excess proliferation of haematopoietic precursors) lead to the abnormal haematological manifestations (neutropenia, thrombocytopaenia, anaemia, etc)
- Excess proliferation of precursors leads to marrow filling up with ‘blast’ cells
- These excess blasts may spill out into peripheral blood, and may be identified on blood film
- Acquisitions of more genetic changes leads to a more complete block of differentiation, exacerbating anaemia etc.
What are the complications of myelodysplasia?
Most serious complications are increased risk of bleeding (due to thrombocytopenia) and increased risk of infection (neutropenia). There is also often anaemia, which can cause iron overload when treated with regular RBC transfusion.
There is increased risk of developing acute myeloid leukemia
What is the basis of diagnosis of MDS?
Early MDS can be difficult to diagnose, and there are multiple differentials. Diagnosis is based upon:
- Abnormal blood count
- Dysplastic features on bone marrow aspirate and trephine
- Increased blast count
- Abnormal Karyotype
What is acute myeloid leukemia? Who is affected? What is the aetiology?
A clonal disorder of myeloid progenitor cells which becomes increasingly common with older age. Leads to an infiltration of bone marrow with immature blast cells (>20% BM MNCs are blasts, normally <5%)
Most cases have no identifiable aetiology, though some will evolve from MDS
Describe the clinical features of acute myeloid leukamia (note - these are mostly related to the presentation of pancytopaenia)
- Anaemia - pale, tired
- Thrombocytopenia - bleeding and bruising
- Neutropenia - infection
- Catabolic state - weightloss, fever, sweats
- Organ infiltration - hepatosplenomegaly, gingival hypertrophy, CNS infiltration
How is acute myeloid leukaemia classified?
AML is defined as having >20% myeloid blasts in bone marrow. Further classification is based upon genetic and cytogenetic abnormalities, as well as on morphology (M0-M7)
It is important to distinguish acute myeloid leukaemia from acute lymphoid leukaemia as treatment and management differ. In cases where morphological abnormalities are insufficient for definitive diagnosis, what tests should be performed?
- Key test is immunophenotyping: FACS is used to confirm blasts are myeloid rather than lymphoid
- Bone marrow may also be sent for cytogenetics. The result has major impact on clinical outcomes
What is the treatment for AML?
In fit patients, combination chemotherapy is used with the aim of complete remission. If this fails, bone marrow transplantation is considered in some patients.
In unfit patients, supportive care and palliative chemotherapy are given. Survival is only 2-3 months.
It is important to identify the M3 variant acute promyelocytic leukaemia early (APL). Why is this?
Malignancy of promyelocytes, containing abundant granules and numerous auer rods. Spontanoeous release of granules, or relase in response to cytotoxic therapy, produces uncontrolled activation of the fibrinolytic system and DIC.
Treatment with alltrans-retinoic acid limits risk of DIC, increases chance of achieving remission
The myeloproliferative disorders are a group of diseases that increase proliferative activity, but have fairly normal maturation, unlike myelodysplastic syndrome or acute myeloid leukaemia. What are the 4 chronic myeloproliferative diseases?
- Chronic myeloid leukaemia
- Polycythaemia Vera
- Essential Thrombocythaemia
- Myelofibrosis
What is chronic myeloid leukaemia? Who is affected, and what is the underlying pathology?
CML is a form of leukaemia characterised by increased and unregulated growth of myeloid cells in the bone marrow, and accumulation of these cells in the blood.
It is very rare in children, but increases in incidence with age
CML is associated with a pathognomic chromosomal rearrangement in which there is reciprocal translocation between chromosome 22 and chromosome 9 (BCR-ABL)
How do patients with CML present? What are the laboratory findings?
Commonest signs are CML are pallor and sometimes massive splenomegaly. Occasionally, the high white count can cause hyperviscosity, leading to priaprism, tinitus and stupor.
Laboratory findings are of anaemia with a vastly elevated white count, particularly of the myeloid lineage. Bone marrow is hypercellular, with increased white cell production.
Describe the clinical course of CML
- Chronic phase - normal blood counts are achieved with therapy, patient is generaly well. This may continue for many years. This eventually transforms into an
- Accelerated phase, and later into a
- Blast crisis, defined by increasing blasts in bone marrow, similar to acute leukaemia. Patients describe weightloss, night sweats and fevers
What is the treatment for CML?
Majority of patients respond to imatinib therapy with normalization of blood counts. 80% achieve a cytogenetic remission for many years.
What is polycythaemia vera? Who is affected, and what is the underlying genetic abnormality
Clonal disorder characterized by excessive proliferation of multipotent haematopoietic stem cells, resulting in an increased number of red cells (often accompanied by an increase in white cell and platelet counts)
Has an insidious onset, usually presenting late in life.
90% of cases are associated with JAK2 mutation
Describe the clinical features of polycythaemia vera
May be asympomatic and an incidental finding on FBC. Other symptoms are related to considerable rise in red cell cound, leading to increased viscosity. These include:
- Headache
- Dizziness
- Stroke / Thrombosis (mesenteric, splenic or portal thrombosis should alert to possibility of PRV)
- Erythromelalgia
- Aquagenic pruritis (itching after hot baths characteristic symptom)
- Splenomegaly and hepatomegaly common
Describe the laboratory findings and management of polycythaemia vera
- Main laboratory finding is increased red cell cound and haemoglobin concentration. There is also frequently raised white cell count, and 50% will have thrombocythaemia
- 90% of patients will have a JAK 2 mutation
- Mainstay of treatment is venesection to reduce haematocrit, and may be combined with aspirin treatment. The aim is to minimise risk of thrombotic events
What is essential thrombocythaemia? Who is commonly affected?
A clonal myeloproliferative disorder chiefly involving the megakaryocyte cell line. It is clasically associated with a marked rise in platelet count, with white cell and haemoglobin counts usually normal
Median age is 60 years, though there is a second peak in women over 30 years of age
Describe the clinical presentation of essential thrombocythaemia
Approximately 60% of patients are asymptomatic and diagnosed on the basis of incidental findings during an FBC. In others, clinical presentation relates to thrombotic complications:
- Erythromelalgia and digital ischaemia. Pain increased by exercise and warmth. Extremities are warm with mottled erythaemia
- Stroke
- Hepatic and portal venous thrombosis
The diagnosis of essential thrombocythaemia is one of exclusion. What 4 diagnostic criteria must be met?
- Sustained elevated platelet count
- Bone marrow biopsy showing mainly proliferation of megakaryocyte lineage
- Not meeting criteria of other myeloproliferative diseases
- Either demonstration of JAK2 mutation (present in 50% of cases) or no evidence of reactive thrombocythaemia
What is the treatment for essential thrombocythaemia?
Generally, treatment is ill-defined. Patients may be asymptomatic, and most authorities suggest a risk based approach. Agents used include:
- Oral chemotherapy with busulphan
- Alpha-interferon to reduce platelet count (side-effects)
- Antiplatelet drugs (e.g. aspirin) an reduce risk of thrombotic episodes
What is primary myelofibrosis? Who does it commonly affect? What is the aetiology?
Clonal disorder of haematopoietic stem cells which results in fibrosis of bone marrow. The fibrosis is reactive, and thought to be secondary to abnormal haematopoiesis.
Typically a disease of the elderly occuring after the age of 50, though rarely presents in children
Approximately 50% of patients have JAK 2 mutations, however overall aetiology poorly understood.
Describe the clinical features of primary myelofibrosis.
- Splenomegaly occurs in 90% of cases, and may be associated with pain
- 50% have hepatomegaly
- Systemic symptoms include weight loss, pallor, night sweats and gout (a consequence of hyperuricaemia from high cell turn over)
Describe the laboratory findings in myelofibrosis. What is the classic feature seen on blood film?
- Patients have a normochromic, normocytic anaemia
- Leukocytosis and thrombocytosis are common, though white cell count is not as high as usually reached in CML
- Bloodfilm typically shows presence of teardrop poikilocytes. This is due to shearing of RBCs in the fibrosed marrow.
- Bone marrow aspiration / trephine is essential for diagnosis - biopsy shows myeloproliferation with granulocytic and megakaryocytic hyperplasia, together with dense fibrosis
What are the complications of primary myelofibrosis? What are the treatments?
- Risk of infection and bleeding, 20% evolve to acute leukemia within 10 years
- Many become transfusion dependent - iron overload of tissues may occur
- Only curative treatment is allogeneic stem cell transplantation
What is Hodgkin’s lymphoma? Who does it affect, and what risk factors have been identified?
- A malignancy or lymphocytes characterized by the presence of low numbers of Reed-Sternberg cells (giant cells derived from B Cells). These are bi- or multi-nucleate, with each nucleus containing a prominent nucleolus.
- Incidence highest in 15-35 year olds
- There is some evidence that Epstein Barr virus plays a role in the pathogenesis of Hodgkin Lymphoma
What is the clinical presentation of Hodgkin’s lymphoma?
Presenting symptoms are similar to non-Hodgkin lymphoma:
- Usually presents with a mediastinal or neck mass. Spread is along lymph vessels, there is frequently contiguous lymph node involvement
- May have other ‘B symptoms’ or sweats, fever, weight loss and pruritis
- Alcohol-induced pain in affected lymph nodes is diagnostic
How is the diagnosis of Hodgkin Lymphoma made?
- Diagnosis is made by lymph node biopsy: either excision biopsy or core biopsy. Fine needle aspirate cannot diagnose or exclude lymphoma.
- Biopsy demonstrates sclerosed lymph nodes with inflammatory infiltrate and bi-nucleate Reed-Sternberg cells
- Lymph nodes which hav ebeen palpable for > 6 weeks require investigation by biopsy
What is the treatment for Hodgkin’s lymphoma? What is the prognosis?
- Treatment with combination chemotherapy +- radiotherapy
- Cure rate > 80%, however secondary malignancies from late effects of treatment an increasing concern
What laboratory findings would be expected in a patient with acute lymphoblastic leukaemia?
-
Pancytopaenia
- Anaemia
- Leukopenia
- Thrombocytopenia
- Blood film showing circulating blast cells
- Bone marrow heavily infiltrated with blast cells
N.B - Laboratory findings are extremely similar to AML - differentiate by immunophenotyping
How is the diagnosis of diffuse large B-cell lymphoma made?
- Core needle biopsy demonstrates diffuse infiltration by large, pleomorphic lymphoid positive cells
- Immunohistochemical staining shows a distinct phenotype, particularly CD20+
What is a Burkitt’s Lymphoma? Who does it typically affect and what are the risk factors?
- High grade clonal lymphoproliferative disease of B-Cells, occuring more commonly in africa though sporadic forms occur in the west.
- Associated with infection by EBV and HIV, more common in men than women
Describe the clinical presentation of Burkitt Lymphoma. What is the common histological sign for diagnosis?
Typically pressents with common B cell symptoms:
- Fever
- Night sweats
- Unexplained lymphadenopathy
- Unexplained weight loss
Core biopsy shows a classic ‘starry sky’ histology, due to macrophages embedded in monomorphic lymphoid infiltrate
Describe the laboratory findings expected in CLL
- Blood film shows small mature lymphocytes and smear cells
- Anaemia and thrombocytopenia is advanced disease
- Hypogammaglobulinaemia is a common finding
- Immunophenotyping shows specific pattern of expression
- Bone marrow aspirate and trephine demonstrate the extent of bone marrow infiltration
Myelomas are often associated with the production of paraproteins (M-proteins). What is a paraprotein, and how are they detected in the laboratory?
Paraproteins are immunoglobulins or immunoglobulin light chains that are produced in excess by clonal proliferation of plasma cells.
They are seen as a narrow band on electrophoresis due to the clonal origin of the cell. They may be found in blood or serum.
Monoclonal free light chains found in blood or serum are called Bence Jones proteins, and may suggest Waldenstroms macroglobulinaemia or myeloma
What are the clinical features of multiple myeloma?
- Calcium elevation (due to breakdown of bone)
- Renal disease (chronic failure from obstruction of distule tubule by proteinaceous casts. Light chains may also have toxic effects on the kidney)
- Anaemia (usually normocytic or macrosytic due to bone marrow failure. Often neutropenia and thrombocytopenia also present)
- Bone disease (bone pain, usually over the lumbar spine is most common presenting feature. Pathological fractures common)
Also: M-protein often > 30g/L and clonal plasma cells >10% in bone marrow
What laboratory findings are present in multiple myeloma?
- Pancytopaenia in advanced disease, normochromic, normocytic or macrocytic anaemia is common
- Blood film shows increased tendency to form rouleaux
- ESR usually raised
- Bone marrow aspirate contain greatly increased proportion of plasma cells
- Electrophoresis demonstrates a discrete band (M-band) of monoclonal immunogloulin
- A free-lite assay may detect Bence-Jones in serum (though the majority are filtered by the kidney to the urine)
What is Waldenstrom’s macroglobulinaemia? Who does it affect and what can the symptoms be attributed to?
A lymphoma of B cells sharing characteristics with other low grade Non-hodgkin lymphomas, caused by hyperproliferation of terminally differentiated B cells. The paraproteinaemia of Waldenstrom’s is almost always associated with IgM
Incidence increases with age, there is a familial disposition and it is commonly associated with HCV infection
Presenting symptoms usually related to hyperviscosity stndrome caused by high serum IgM
What laboratory findings are made in Waldenstrom’s macroglobulineamia?
- Anaemia, Leukopenia and Thrombocytoenia
- Lymphocytosis may be present
- IgM Monoclonal protein band
- Bone marrow infiltration with lymphoid cells
- Bence-Jones proteins may be present in serum and urine
What is haemolysis? What are the clinical features that indicate haemolysis is occuring?
Haemolysis is the rupture of erythrocytes and release of their contents into serum. It is associated with:
- Pallor and jaundice (due to anaemia and increased serum unconjugated bilirubin
- Splenomegaly (chronic haemolysis may cause extramedullary haematopoiesis)
- Chronic haemoloysis may also cause
- Pigment gallstones
- Leg ulcers
- Marrow expansion (marrow physically expanding due to increased haematopoiesis)
What laboratory features are present in hereditary spherocytosis?
- Presence of spherocytes (RBCs lacking central area of pallor due to loss of skeletal integrity and biconcave shape) in peripheral blood film
- Increased reticulocyte count
- Raised plasma bilirubin
- Negative direct antiglobulin test (to exclude autoimmune causes)
- Increased osmotic fragility of red cells (cells are thicker than usual, smaller amount of fluid uptake than usual required for lysis of cells.)
What is the treatment for hereditary spehrocytosis?
- Folic acid supplementation (used in treatment of all chronic haemolytic anaemias - chronic haemolytic disease rapidly depletes folate stores)
- Consider splenecomy, particularly in severely anaemic children or those with complications such as gall stones. This should be delayed until after the age of 10 if possible, to reduce risk of fatal infection from capsulated bacteria
What is Glucose-6-Phosphate Dehydrogenase deficiency, who does it affect and what is the aetiology?
G6PD is an enzyme involved in the pentose-phosphate shunt, required for respiration in red blood cells. Reduced activity of G6PD results in reduced concentrations of reducing compounds GSH and NADPH, leading to increased retention and elimination within the spleen.
400m sufferers worldwide, however, mostly symptomless. Infection or exposure to oxidant stressors can lead to acute episodes of haemolysis and anaemia
Defective gene found on X chromosome, therefore most likely to affect males
How is the laboratory diagnosis of G6PD made?
- Denatured methaemoglobin precipitates into red cell forming rounded masses - Heinz bodies - which are visible on blood film
- Haptoglobin levels are lowered in an acute episode, as both intra- and extravascular haemolysis occurs
- Coombs’ test negative - exclude immune causes
- G6PD enzyme levels lowered, though this can be difficult to assess in acute phase, as enzyme levels are higher in reticulocytes
Blood films of cold AIHA and warm AIHA show different red cell characteristics. Warm AIHA has a film with reticulocytes and spherocytes (below). How is the film of cold AIHA different?
Cold AIHA - prominenet red cell agglutination due to the cross linking activity of multimeric IgM antibodies.
Autoimmune haemolytic anaemia is diagnosed using the Direct Coombs est. How does this test work?
- Detects for the presence of erythrocytes coated in antibody
- Blood sample is taken and washed, and anti-human globulin added to bind any immunoglobulin bound to RBCs
- A positive result is red cell agglutination, showing autoimmune haemolytic anaemia
What are the main causes of warm and cold AIHA
Warm AIHA:
- Idiopathic
- Secondary to SLE, CLL or Lymphoma
Cold AIHA
- Idiopathic
- Secondary to infection with Mycoplasma pneumoniae, infectious mononucleosis, lymphoma
Both may rarely be caused by drugs, such as penicillin or methyldopa
An alloimmune cause of haemolytic anaemia is haemolytid disease of the newborn. Describe the steps that lead to a child with rhesus disease?
- RhD+ cells of the foetus cross the placenta (either by trauma, or naturally within the third trimester), resulting in immunisation of the mother
- IgG antibodies cross the placenta and react with fetal erythrocytes in subsequent pregnancies
- Children are born with jaundice and anaemia due to intravascular haemolysis
A non-immune cause of haemolytic anaemia is microangiopathic haemolytic anaemia (MAHA). What underlying conditions may cause MAHA? What is the characteristic blood film finding?
Underlying pathology is of any disease which may impact small vessels leading to mechanical shearing. As a result, schistocytes (fragmented red cells) may be seen on blood film. Causes include:
- Haemolytic uraemic syndrome
- Thrombotic thrombocytopenic purpura
- Metastatic malignancy
- Malignant hypertension
- DIC
Globin chains are synthesized from an alpha cluster on chromosome 16 and a b cluster on chromsome 12. In diploid cells, there are 4 alpha and 2 beta genes. However, other arrangements can be made. What blood types make up normal blood?
- 98% HbA - formed from 2α and 2β globin chains (central spike on HPLC)
- 1% HbF - formed from 2α and 2γ globin chains
- <3.5% HbA2 - formed from 2α and 2δ
What findings (laboratory and clinical) would be expected in a patient with HbH disease?
- Blood film shows microcytic, hypochromic cells with target cells and Heinz bodies
- Patients are hypersplenic and anaemic
What is the genetic basis of transmission of α and β thalassaemia?
Both transmitted in an autosomal recessive fashion.
How is the diagnosis of sickle cell anaemia made?
- Blood film shows ‘pencil’ shaped sickled cells, along with a microcytic, hypochromic anaemia
- Electrophoresis shows a single major band in the HbS position
- Screening test shows the presence of HbS in both parents
What is a venous thromboembolism? What factors predispose to developing VTE?
A venous thrombus is a clot occuring within the deep veins of the leg, which has the potential to break off and embolize to the lungs.
Acquired risk factors for VTE:
- Age
- Malignancy
- Surgery / trauma
- Immobilization
- Oral contraceptive / HRT
- Lifestyle choices: smoking, obesity
- Antiphospholipid syndrome
Congenital risk factors for VTE
- Factor V leiden
- Antithrombin deficiency
- Protein C/S deficiency
Describe the signs of a pulmonary embolism
- Shortness of breath
- Pleuritic chestpain
- Tachycardia
- Haemoptysis
- Circulatory collapse
