Haematology Flashcards
(97 cards)
1
Q
What are the key steps controlling Hb production
A
- 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
2
Q
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?
A
- 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
3
Q
Anaemias are classified by mean corposcular volume (MCV) and mean cell haemoglobin (MCH). What are these classifications?
A
- Low MCV and Low MCH - Microcytic anaemia
- High MCV - Macrocytic anaemia
- Normal MCV and MCH - Normochromic normocytic anaemia
4
Q
What are the two causes of microcytic anaemia?
A
- Iron deficiency: This in itself has many causes
- Thalassemia trait: formation of abnormal Hb molecules leads to excess destruction of RBC and resulting anaemia
5
Q
What are the 4 main causes of Fe2+ deficiency leading to a microcytic anaemia?
A
- 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
6
Q
What is normocytic anaemia? What are the causes?
A
- The anaemia of chronic disease, associated with a MCV within normal range, and normal MCH (normochromic)
- Caused by chronic infection, inflammation, malignancy, renal failure
7
Q
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
A
8
Q
What is myelodysplasia (myelodysplastic syndrome)? Who does it typically present in?
A
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.
9
Q
How will patients with myelodysplasia present? Describe the typical laboratory features.
A
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.”
10
Q
How does the pathological change in MDS (excess proliferation of haematopoietic precursors) lead to the abnormal haematological manifestations (neutropenia, thrombocytopaenia, anaemia, etc)
A
- 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.
11
Q
What are the complications of myelodysplasia?
A
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
12
Q
What is the basis of diagnosis of MDS?
A
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
13
Q
What is acute myeloid leukemia? Who is affected? What is the aetiology?
A
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
14
Q
Describe the clinical features of acute myeloid leukamia (note - these are mostly related to the presentation of pancytopaenia)
A
- Anaemia - pale, tired
- Thrombocytopenia - bleeding and bruising
- Neutropenia - infection
- Catabolic state - weightloss, fever, sweats
- Organ infiltration - hepatosplenomegaly, gingival hypertrophy, CNS infiltration
15
Q
How is acute myeloid leukaemia classified?
A
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)
16
Q
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?
A
- 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
17
Q
What is the treatment for AML?
A
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.
18
Q
It is important to identify the M3 variant acute promyelocytic leukaemia early (APL). Why is this?
A
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
19
Q
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?
A
- Chronic myeloid leukaemia
- Polycythaemia Vera
- Essential Thrombocythaemia
- Myelofibrosis
20
Q
What is chronic myeloid leukaemia? Who is affected, and what is the underlying pathology?
A
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)
21
Q
How do patients with CML present? What are the laboratory findings?
A
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.
22
Q
Describe the clinical course of CML
A
- 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
23
Q
What is the treatment for CML?
A
Majority of patients respond to imatinib therapy with normalization of blood counts. 80% achieve a cytogenetic remission for many years.
24
Q
What is polycythaemia vera? Who is affected, and what is the underlying genetic abnormality
A
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
25
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
26
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
27
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
28
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
29
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
30
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
31
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.
32
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)
33
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**
34
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
35
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
36
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
37
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
38
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
39
B-Cell non-Hodgkin lymphoma can be divided into high grade and low grade. What are the main high grade and low grade categories?
High grade:
* Diffuse large B cell lymphoma
* Burkitt Lymphoma
* Lymphoblastic lymphoma
Low grade:
* Chronic lymphoid leukaemia
* Follicular lymphoma
* Marginal zone lymphoma
40
Compare the features of high and low grade B-cell non-hodgkin lymphoma (e.g. rate of progression, survival without treatment, etc)
High grade:
* **Rapid** progression
* Survival without treatment - months
* **Increases with age** but can be seen in children
* Usually no cause - HIV a risk factor
* Frequently **curable** with chemotherapy
Low grade:
* **Slow** progression
* Survive without treatment - years
* **Increases with age** - never seen in children
* Usually no cause (though *H pylori* in gastric MALT lymphoma
* Generally **NOT curable** with chemotherapy
41
What is acute lymphoblastic leukaemia, and who does it most commonly affect? What similarities does it share with acute myeloid leukaemia, and how are they differentiated?
A leukaemia characterised by **excess lymphoblasts.** Malignant, immature white cells are continuously multiply and are overproduced in the bone marrow. Most commonly affects children, with a peak between 1-9 years
Bone marrow smear from both **ALL and AML have \>20% infiltration of blast cells**, which are also present in the peripheral blood. The disorders are therefore separated by **immunophenotyping** of blast cells to define lineage
42
Describe the clinical features of acute lymphoblastic leukaemia (clue - related to bone marrow failure secondary to bone marrow infiltration)
* Weakness and tiredness
* Bruising and bleeding, secondary to thrombocytopenia, petechial haemorrhages
* Ottitis media, pneumonia, pharyngitis caused by profound neutropenia
* Bone pain
* Lymphadenopathy
43
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**
44
What prognostic factors determine the outcome of ALL? What is treatment goal?
* Poor prognostic factors include **high WCC** at presentation, specific c**ytogenetic abnormalities** (e.g. philadelphia chromosome), male sex
* Treatment involves **multi-agent chemotherapy** over a period of years. High levels of steroids leads to avascular necrosis of the femoral head and psychiatric disturbances
* **80% cure rate**
45
What is diffuse large B-cell lymphoma? Who does it usually present in, and what risk factors have been identified?
* The most common non-hodgkin lymphoma among adults, DLBCL is an **agressive, high-grade tumour of B cells** which may arise anywhere in the body. It is characterised by **large cells of B-cell origin**
* Occurs in all age groups, but is much **commoner in older age**
* Underlying immunodeficiency such as **AIDS** is an important risk factor.
46
What are the clinical signs associated with a diffuse large B-cell lymphoma?
Typically present with a **rapidly growing mass of nodal origin** (as other high-grade lymphomas). May also have:
* Weight loss
* Fever
* Night sweats
* **Extranodal lymphoma** involving sites such as the GI tract, testis, brain or bone
47
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+
48
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
49
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
50
What is B-cell chronic lymphocytic leukaemia? Who does it affect and how common is it?
Neoplastic disorder characterized by the **accumulation of small mature lymphocytes in the blood, bone marrow and lymphoid tissue**. Affects almost exclusively adults \> 50 years, and is the most common adult leukaemia in the western world
51
Describe the clinical features of chronic lymphocytic leukaemia
* Many patients **asymptomatic** at diagnosis - incidental finding
* May present with symptoms attributable to **anaemia** - tiredness and fatigue
* Bruising and bleeding secondary to **thrombocytopaenia**
* Sinusitis and bacterial pneumonia may occur secondary to **hypogammaglobulinaemia**
* Lymphadenopathy and hepatosplenomegaly common
52
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
53
Most lymphomas are staged using the Ann Arbor classification system. What are the characteristics of each stage (I - IV), and what defines the A and B subtypes of each classification?
1. Involvement of one lymph node area
2. Involvement of two or more lymph node areas on the same side of the diaphragm
3. Involvement of lymph nodes on both sides of the diaphragm, with or without involvement of the spleen
4. Involvement of one or more extranodal sites (e.g. liver, marrow, lung)
A - without systemic symptoms
B - with systemic symtpoms (night sweats, fever, weight loss etc)
54
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**
55
What is monoclonal gammapathy of undetermined significance? Who is affected, and what are the clinical risks?
* A benign condition associated with the presence of paraproteins in the blood, usually found incidentally
* Incidence 3% in \> 50 year olds, 8% in \>75 year olds. 3-fold increased risk in black populations
* 1-2% risk of progression to myeloma per year
56
What criteria must be fulfilled for a diagnosis of MGUS?
* A monoclonal paraprotein band \<30g/L
* Plasma cells \<10% on bone marrow examination
* No evidence of bone lesions, hypercalcaemia, anaemia or renal insufficiency related to the paraprotein
* No evidence of another B cell proliferative disorder
57
What is multiple myeloma? Who does it commonly affect, what are the risk factors?
Disease arising from malignant transformation of a B cell. The differentiating cells of the **malignant clone** have the morphology of **plasma cells**. and **secrete rearranged monoclonal immunoglobulin** (either IgG or IgG, a monoclonal light chain or both)
Median age of onset is **65-70** years, more commonly affects black populations that white
Thought to **follow from MGUS** in all patients, however, since MGUS is usually asymptomatic, this is difficult to detect
58
What are the clinical features of multiple myeloma?
* **C**alcium elevation (due to breakdown of bone)
* **R**enal disease (chronic failure from obstruction of distule tubule by proteinaceous casts. Light chains may also have toxic effects on the kidney)
* **A**naemia (usually normocytic or macrosytic due to bone marrow failure. Often neutropenia and thrombocytopenia also present)
* **B**one 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
59
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)
60
What is the treatment of multiple myeloma? What is the prognosis?
* Myeloma is **incurable**. Prognosis is related to serum levels of **β2 microglobulin** (corelates with tumour mass and rate of turnover). With conventional treatment, median survival is 3-4 years
* Supportive care is used to reduce risk of **hyperviscosity syndrome** due to high levels of paraproteins. Bacterial infections require prompt treatment to avoid **neutropenic sepsis**. Bisphosphates reduce bone pain and progression to **skeletal lesions**
* Chemotherapy and radiotherapy are used to relieve symptoms
61
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
62
Describe the clinical presentation of Waldenstroms
* Headaches and visual disturbances, some times strokes. Due to **hyperviscosity**
* **Tiredness and fatigue**, often disproportionate to the level of **anaemia**
* Systemic symptoms such as fever, weight loss and night sweats are associated with **high-grade transformation** of the lymphoma
63
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
64
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)
65
What laboratory findings are expected in a patient presenting with haemolysis?
* **Elevated unconjugated bilirubin** - overload of hepatic metabolism causes build of unconjugated bilirubin
* **Elevated LDH** - lysing RBCs spill LDH into serum
* **Elevated reticulocyte count** - BM response to falling Hb, may also be nucleated red cells in peripheral blood
* **Mildly macrocytic anaemia** - reticulocytes spill over into peripheral blood. They are larger than normal RBCs thus MCV is increased
66
Haemolysis may take place intravascularly, or extravascularly within the reticular endothelial system. What biochemical evidence signals intravascular or extravascular haemolysis is occuring?
Intravascular haemolysis:
* Hb released directly from RBCs into serum. Hb binds to haptoglobin, but quickly saturates the system. This leads to:
* Decreased serum haptoglobin
* Haemoglobinaemia
* Haemoglobinuria
Extravascular haemolysis
* RBCs destroyed in macrophages in the spleen, thus haem is converted to bilirubin and attached to albumin for transport to the liver
* Falls in haptoglobin less marked
* Free haemoglobin is not found
67
The causes of haemoloysis can be divded into congenital and acquired (which may itself be further subdivided into immune and non-immune mechanisms). What are the main causes in each of these categories?
Congenital - defects in the main components of the red cell:
* Membrane (e.g. hereditary spherocytosis)
* Haemoglobin (haemoglobinopathies, thalassemia syndromes)
* Enzymes (G6PD deficiency)
Acquired
* Immune:
* Autoimmune
* Alloimmune
* Non-autoimmune
* Mechanical
* Microangiopathic haemolytic anaemia
* Infection
68
What is hereditary spherocytosis? Who gets it, and what is the underlying abnormality?
Hereditary spherocytosis is a **congenital** haemolytic anaemia, caused by **mutations in the cytoskeletal proteins** of erythrocytes (most commonly ankyrin). The cells produced are less deformable than normal erythrocytes, and are therefore **retained and destroyed by splenic macrophages** during circulation.
Usually inherited in an **autosomal dominant** manner, thus a family history is important for defining disease.
69
How does hereditary spherocytosis present?
* **Anaemia** (tiredness, pallor etc)
* **Jaundice** and splenomegaly are common.
* Most patients develop **pigment stones** in the gall bladder, and 10-20% with intact spleens may also develop acute cholecystitis or biliary obstruction
* Viral illnes may lead to episodes of increased destruction - increased anaemia and jaundice
70
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.)
71
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
72
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
73
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
74
Autoimmune causes of haemolytic anaemia can be divded into those mediated by "warm" reactive antbodies, and those mediated by "cold" reactive antibodies. What is the difference between the two?
Warm AIHA (antibodies react best at 37°C)
* **IgG** or complement mediated. Components opsonize erythrocytes for phagocytosis by splenic macrophages
* Often idiopathic, but may be a secondary consequence of other autoimmune diseases (e.g. SLE) or lymphoproliferative disease
Cold AIHA (antibodies react best at 32°)
* IgM mediated
* Worse in cold weather and in the peripheries - leads to acrocyanosis (coldness, purplish discoloration and numbness of fingers, toes, ear lobes and nose)
* Symptoms due to formation of red cell agglutinates in skin and red cell lysis
75
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.
76
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
77
What treatment is given for autoimmune haemolytic anaemia?
* Treatment for warm AIHA usually starts with steroids, but other forms of immuno suppression may need to be considered
* Folate supplementation is given (as in all haemolytic disease)
* Blood transfusion is aoivded if possible
78
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
79
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
80
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
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Globin disorders such as thalassaemia or sickle cell disorder are a congenital cause of haemolytic anaemia. They are either qualitative or quantitative disorders: which categories do sickle cell and thalassaemia fall into, and what is the underlying pathology in each case?
Quantitative disorder - a reduction in the quantity of globin chains produced
* Thalassaemia - defects in either the α (deletion) or β globin genes (point mutation), leading to an imbalance of α and β chain synthesis
Qualitative disorder - a structural variant of the chains produced
* Sickle cell anaemia - structural defect in the β globin gene, resulting in deformation, increased rigidity and destruction of erythrocytes
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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
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Alpha thalassaemia is caused by a deletion in the α-globin genes. There are 4 genes in diploid cells, and thus there may be a deletion of between one and four α-chains. What pathology is seen in the absence of 1,2,3 or 4 α-chains?
* 1 - **minimal effect** - 3α genes are sufficient to permit normal Hb formation with no clinical symptoms
* 2 - **α thalassaemia trait**. 2 remaining genes permit nearly normal haematopoiesis, may have a mild microcytic hypochromic anaemia, but clinically silent
* 3 - **Haemoglobin H disease**. In the absence of sufficient α chains, a **tetrameric β chain** is formed. There is a microcytic, hypochromic anaemia
* 4 - **Hydrops fetalis** (non-viable). Cannot survive post-partum, many die in utero
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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
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Unlike α thalassaemia, which is caused by deletion of α chain genes, β thalassaemia is caused by a large number of mutations which may either cause non-deletion or deletion of the β chain genes. What phenotypes of β thalassemia exist, and which haemoglobin forms predominate in each case?
* β-thalassaemia minor - only one β chain is mutated, may have slightly raised HbA2 or HbF and a microcytic, hypochromic anaemia but no severe disease
* β-thalassaemia intermedia - an intermediate condition between minor and major, may be caused by a deletion of one β-chain gene or a mutation in both. Raised HbA2 or HbF as available α chains combine with anything available
* β-thalassaemia major - deletion of both β-globin genes, no HbA. Severe anaemia, require life long transfusion
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What is the management of β-thalassaemia major?
* Regular transfusions to maintain Hb concentration at normal levels
* Splenectomy carried out if there is evidence of splenomegaly and increased transfusion requirement
* Deferasirox (an iron chelator) is used to prevent iron overload by facilitating urinary excretion
* Only treatment is bone marrow transplantation
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What is the genetic basis of transmission of α and β thalassaemia?
Both transmitted in an autosomal recessive fashion.
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What is haemoglobin S (HbS)? How is it inherited? What is the phenotype of heterozygotes and homozygotes?
* HbS is caused by a point mutation in the β globin chain (glutamic acid -\> valine), resulting in an insoluble form of haemoglobin.
* Heterozygotes have sickle cell trait with both HbA and HbS forming. However, due to the lower affinity of βs chains for α chains, HbA \> HbS
* Homozygotes have sickle-cell anaemia, with 'sickled' erythrocytes found in peripheral blood
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What clinical manifestations are seen in sickle cell anaemia?
* **Chronic haemolytic anaemia** and subsequent cholelithiasis (gall stones)
* **Splenic sequestration syndrome** (acute painful enlargement of the spleen due to obstruction of capillaries, risk of infection by capsulated bacteria)
* **Vaso-occlusive crises** (obstruction of capillaries, ischaemia and necrosis of tissue, pain)
* **Aplastic crisis** - acute worsening of baseline anaemia caused by parvovirus infection
* Cerebral infarction, TIA, intracranial haemorrhage
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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
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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
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Describe the clinical presentation of a DVT.
* Pain and tenderness
* Swelling
* Pitting oedema
* Increased warmth
* Collateral superficial veins
* Change in skin colour
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Describe the signs of a pulmonary embolism
* Shortness of breath
* Pleuritic chestpain
* Tachycardia
* Haemoptysis
* Circulatory collapse
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The mainstay of anticoagulation treatment is with heparin (either fractionated, or unfractionated) or warfarin. Describe the action of each of these two treatments
Heparin
* Binds to the enzyme antithrombin, causing a conformational change and potentiating its mechanism of action.
* It has a short half life (1 hour for unfractionated, 4-5h for LMWH) but fast onset of action
Warfarin
* Vitamin K epoxide reductase inhibitor. Vit K is required to perform essential post-translational modifications of clotting factors II (prothrombin), VII, IX and X
* It has a much longer half life (40h), but takes a period of days before effects are seen
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Warfarinised patients are at risk of both non-major and major bleeding. How is warfarin reversed in the situation of bleeding?
Major bleeding:
* Rapid infusion of prothrombin complex concentrates (PCC) - containing factors II, VII, IX and X (i.e. those that are inhibited by warfarins activity) and vitamin K
Non-major bleeding
* Infusion of vitamin K. Takes a period of days to referse the action of warfarin
INR \> 8.0 without bleeding
* Oral vitamin K
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Anticoagulation carries bleeding risk, and therefore therapies must be monitored. How are heparin and warfarin monitored in order to reduce risk of bleeding?
Heparin:
* APTT continously monitored, with infusion adjusted to remain within normal laboratory range.
Warfarin:
* PT expressed as an INR to measure degree of anticoagulation. A reading of \> 4.0 suggests over anticoagulation, and requires reduced therapy
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