Haematology 1 Flashcards
What does myeloid mean?
Of the marrow!
Refers to red cells, platelets, granulocytes and their precursors
Myeloid diseases
Arise clonally within the marrow
e.g acute myeloid leukaemia, chronic myeloproliferative neoplasms
Myeloid cells found in the bone marrow
Myeloblast Promyelocyte Myelocyte Metamyelocyte (band cells)
Myeloid cells found in the blood
(band cells)
Neutrophils
Clonal defect which prevents myeloid maturation
Acute myeloid leukaemia
Clonal defect which causes defective myeloid maturation
Myelodysplastic syndromes
Clonal defect which causes excessive myeloid maturation down one limb of the maturation pathway
Chronic myeloproliferative neoplasms
- Polycythaemia (RBCs)
- Essential thrombocythaemia (Platelets)
- Chronic myeloid leukaemia
- Myelofibrosis
Features of AML
No neutrophils (total development block)
Features of myelodysplastic syndromes
Abnormal cells
e.g granulocytes with no granules
Features of CML
loads of neutrophils
philadelphia chrosome
Eosinophilia associated with
- Allergic states
e. g asthma, dermatitis, drug rashes and with parasitic infections - Vasculitic disorders
- Myeloproliferative disease
Proportion of lymphocytes that are T cells
75%
Ratio of CD4:CD8 cells
2:1
Causes of splenic infarcts
Haematological disorders include:
-polycythaemia -hypercoaguable states (protein C or protein S deficiency, sickle cell disease)
-malignant conditions (lymphomas and leukaemias)
In infiltrative haematological diseases the splenic circulation gets congested by abnormal cells.
Embolic causes:
- atrial fibrillation
- ventricular mural thrombus following a myocardial infarction
- septic emboli from infective endocarditis.
Reed Sternberg cells
Giant cells found in Hodgkin’s lymphoma.
Neoplastic germinal centre-derived B cells
Subtypes of classical Hodgkin lymphoma
- nodular sclerosing (NS) most common
- mixed cellularity (MC)
- lymphocyte-rich (LR)
- lymphocyte-depleted (LD)
Morphology of lymph nodes in Hodgkin lymphoma
Enlarged and sometimes matted together
What are B symptoms?
fever
night sweats
weight loss
Prognositc significance of B symptoms
If untreated, death generally occurs within 6 to 24 months, but with treatment there is an 85% cure rate.
Symptoms of a ruptured spleen
Sudden onset left upper abdo pain.
Symptoms and signs of hypovolaemic shock.
Predisposing factors to splenic rupture
Malaria
Infectious mononucleosis
Lymphomas/leukaemias
Typhoid fever
Precursor of platelets
Megakaryocytes- sheds platelets from cytoplasm
Causes of decreased numbers of platelets
Primary platelet defect Marrow suppression Autoimmune attack Consumption Sepsis
Difference between immunohistochemistry and immunophenotyping
IHC- tend to stain tissue
Immunophenotyping- single cell suspension, generally look for markers on the outside
Reed-Sternberg cells
aka lacunar histiocytes/ owls eyes
seen in Classical Hodgkin lymphoma
Multi-nucleate or multilobate large cell with each nucleus or lobe containing a prominent eosinophilic nucleolus with a modest rim of amphiphilic cytoplasm
Use of FISH
Fluorescence in situ hybridization
Chromosomal abnormalities
FISH can be used to identify missing, duplicated or translocated genetic material
CD20 monoclonal antibody
Rituximab
What type of FISH would you use to detect common translocations in which both partners are known?
Dual colour fusion probe FISH
What type of FISH would be useful if you don’t know the translocation partner?
Dual colour breakapart probe FISH
BCR-ABL tyrosine kinase inhibitor
Imatinib
first-line therapy for most patients with chronic myelogenous leukemia (CML). More than 90% of CML cases are caused by a chromosomal abnormality that results in the formation of a so-called Philadelphia chromosome
What is the Philadelphia chromosome?
Fusion between the Abelson (Abl) tyrosine kinase gene at chromosome 9 and the break point cluster (Bcr) gene at chromosome 22, resulting in a chimeric oncogene (Bcr-Abl) and a constitutively active Bcr-Abl tyrosine kinase that has been implicated in the pathogenesis of CML.
Mutation associated with myeloproliferative disease
JAK2 V617F
Mutation associated with haemochromatosis
HFE C282Y
What’s HFE1?
Hereditary haemochromatosis
Hereditary disease characterized by excessive intestinal absorption of dietary iron resulting in a pathological increase in total body iron stores. Humans, like most animals, have no means to excrete excess iron.
Excess iron accumulates in tissues and organs disrupting their normal function. The most susceptible organs include the liver, adrenal glands, heart, skin, gonads, joints, and the pancreas; patients can present with cirrhosis, polyarthropathy, adrenal insufficiency, heart failure or diabetes.
Function of HFE gene
A working model describes the defect in the HFE gene, where a mutation puts the intestinal absorption of iron into overdrive. Normally, HFE facilitates the binding of transferrin, which is iron’s carrier protein in the blood. Transferrin levels are typically elevated at times of iron depletion (low ferritin stimulates the release of transferrin from the liver). When transferrin is high, HFE works to increase the intestinal release of iron into the blood. When HFE is mutated, the intestines perpetually interpret a strong transferrin signal as if the body were deficient in iron. This leads to maximal iron absorption from ingested foods and iron overload in the tissues.
Mutation associated with alpha-1 antitrypsin deficiency
A1AT G324L
Mutation associated with familial adenomatous polyposis coli
APC
MUTYH
MUTYH glycosylase, involved in oxidative DNA damage repair. Base excision repair
BRCA mutations linked to which cancers
breast
ovarian
prostate cancer
Next generation sequencing based on…
DNA extraction Amplification / library preparation Sequence detection Alignment to a reference sequence Bioinformatics analysis
In what disease dose a translocation between the genes PML and RARA occur? What does the fusion protein do?
Seen in one form of acute myeloid leukaemia (AML) produces a fusion protein that blocks granulocytic differentiation.
Where and when does erythropoiesis occur in the foetus?
- Starts at about 21 days gestation
- Initially in the yolk sac “blood islands”
- Then in the fetal liver
- Then moves to the bone marrow
Where does erythropoiesis occur in the adult?
Restricted to the pelvis, sternum, vertebrae and ends of long bones (femora/humeri)
How many RBCs do we have? How many are produced per hour?
- Adults have approximately 4 x 10^12 red cells per litre of blood
- Each RBC has a normal lifespan of 120 days
- 1% of the total need to be replaced daily to maintain a steady state…
- This equates to 10^10 red cells produced per hour
RBCs found in the blood
Reticulocytes
RBCs
Stages of RBC found in the bone marrow
- CMP
- CFU
- Proerythroblast
- Basophilic erythroblat
- Intermediate erythroblast
- Late erythroblast
What controls the number of RBCs and the amount of haemoglobin? Where is it released from?
EPO (erythropoietin)
Epo is produced by the interstitial cells of the renal cortex, in response to hypoxia.
Stages in RBC production that can go wrong and cause anaemia
Hypoxaemia detected in the kidney (using HIF pathway)
EPO synthesis increased
- Insufficient epo production
Increased red cell synthesis in the marrow
- Lack of the components needed for red cell synthesis
- Defective red cells made?
More oxygen carrying capacity in the circulation
- Red cells lost too soon from the circulation
What does EPO do to the bone marrow?
The loss of oxygen-carrying capacity will cause an increase in Epo synthesis, and there will be erythroid hyperplasia in the marrow until a steady state is reached again.
Why is a reticulocyte count helpful?
An increased reticulocyte count demonstrates that the process of erythropoiesis is still intact, and that the marrow is responding to the loss of red cells.
This is a useful parameter for determining whether anaemia is due to increased consumption or impaired production.
Dietary components needed for RBC synthesis
Iron
Folate
B12
How is iron absorbed from the gut?
Binds to divalent metal transporter 1 (DMT1).
Allowed out of the cell by ferroportin.
In the digestive tract, it is located on the apical membrane of enterocytes, where it carries out H+ coupled transport of divalent metal cations from the intestinal lumen into the cell.
DMT1 expression is regulated by body iron stores to maintain iron homeostasis.
Ferroportin is a transmembrane protein that transports iron from the inside of a cell to the outside of the cell. After iron is absorbed into the cells of the intestine, ferroportin allows that iron to be transported out of those cells and into the bloodstream.
How is ferroportin inhibited?
Ferroportin is inhibited by hepcidin, which binds to ferroportin and internalizes it within the cell. This results in the retention of iron within enterocytes, hepatocytes, and macrophages with a consequent reduction in iron levels within the blood serum. This is especially significant with enterocytes which, when shed at the end of their lifespan, results in significant iron loss. This is part of the mechanism that causes anaemia of chronic disease; hepcidin is released from the liver in response to inflammatory cytokines, namely interleukin-6, which results in an increased hepcidin concentration and a consequent decrease in plasma iron levels.
How does iron deficiency occur?
Not ingesting enough/increased requiremetnt
- limited diet in elderly, vegetarians/vegans (haem iron is more readily asorbed than non-haem iron), pregnancy, toddlers
Not absorbing enough
- Coeliac disease (iron absorbed in duodenum), gastrectomy (HCl needed to solublise iron)
Increased iron loss
- GI bleed (gastric or colon cancer), gynae bleeding (menorrhagia)
Characteristic changes in the blood in iron deficiency
- Low MCV (microcytosis)
- Low MCH (hypochromia)
- Variation in the size and shape of the red blood cells (anisocytosis and poikilocytosis).
- Some red cells become pencil shaped.
- The reticulocyte count will not be as high as expected.
How to investigate iron deficiency
- Serum iron
decreased in iron deficiency; however is subject to acute variation due to dietary intake, and also falls in infection/inflammation - Transferrin
the circulating iron transport protein and has two binding sites for Fe+++ . The level is raised in iron deficiency. The serum transferrin is frequently reduced in patients with inflammatory arthritis and malignancy. - Serum ferritin
levels roughly correlate with the amount of tissue storage iron when the serum ferritin is below 2000 mg/l.
Serum ferritin levels are low in iron deficiency but there is much variation: ferritin also acts as an acute phase protein, rising in infection and inflammation.
Function of B12
B12 is needed for nucleic acid synthesis, and is also thought to be needed for myelin maintenance.
How and where is B12 taken up?
Absorption is dependent on binding to intrinsic factor, which is produced by the
parietal cells of the stomach.
The B12-IF complex absorbed in terminal ileum.
How does vitamin B12 deficiency occur?
Not ingesting enough/increased requiremetnt
- very limited diet (elderly), vegetarians/vegans (B12 found exclusively in animal sources), pregnancy
Not absorbing enough
- pernicious anaemia (autoimmune gastritis of lack of IF)
- gastrectomy or atrophic gastritis (lack of IF)
- pancreatic disease, pancreatectomy
- crohn’s disease
- ileal resection
- tropical sprue
Characteristic changes in the blood in B12 deficiency:
Anaemia with a high MCV (macrocytosis), red cells often oval
The neutrophil count and platelet count may also be reduced
Hypersegmented neutrophils
The reticulocyte count will
not be as high as expected.
Clinical features of B12 deficiency
Glossitis
Peripheral neuropathy
Dorsal column involvement
Investigations for B12 deficiency
• Serum B12
If pernicious anaemia:
• Anti-intrinsic factor antibodies
• Anti-gastric parietal cell antibodies
• Further GI/pancreatic assessment if needed.
What’s folate needed for?
Folate is important for the donation of single carbon units, i.e. methyl groups, to make amino acids. It is required in the synthesis of pyrimidines and purines of nucleic acid, and therefore deficiency has
some similarities to B12 deficiency
What’s folate destroyed by?
Heat
Who might require extra folate?
Pregnant or breast feeding women
Clear and important relationship between folate deficiency and neural tube defects in pregnancy – supplementation recommended.
Where is folate absorbed?
Jejunum (coeliac patients at risk of deficiency)
How does folate deficiency arise?
Not ingesting enough/increased requiremetnt
- very limited diet (elderly)
- patients on dialysis
- increased desquamation (exfoliative dermatitis)
- pregnancy
Not absorbing enough
- coeliac disease
Anti-folate medications
- methotrexate
- anti-convulsants
Characteristic changes in the blood in folate deficiency:
Anaemia
High MCV
White count and platelet count may be low
What can cause a lack of red cell precursors or marrow space?
Loss of early red cell precursors or haemopoietic stem cells (e.g. aplastic anaemia) can limit erythropoiesis
Obliteration of the marrow space (e.g. by metastatic malignancy) can mean erythropoiesis is suppressed.
What can nucleated RBCs in the blood indicate?
Marrow stress e.g infiltration
Fate of defective red cells?
Early destruction
e.g thalassaemia myelodysplastic syndromes
How can kidney disease cause anaemia?
Lack of EPO production
Anaemia of chronic disease and iron
- Also known as the anaemia of inflammation
- Complex mechanism, still not fully understood.
- Characterised by mis-handling of iron
- Increased levels of the master iron regulatory protein hepcidin
- Relatively suppressed epo production
- Relatively suppressed response to epo stimulation
- Frequently seen in chronic inflammatory conditions such as rheumatoid arthritis and in some cancers.
Clinical features of anaemia of chronic disease
Often a mild anaemia (Hb usually 80g/L or higher)
Typically normal MCV (sometimes microcytic)
Iron studies can be hard to interpret, but typically:
- Low serum iron
- High or normal ferritin
- Low transferrin
What does the following indicate?
Iron low
Transferrin high
Ferritin low
Iron deficiency anaemia
What does the following indicate?
Iron low
Transferrin low
Ferritin normal/high
Anaemia of chronic disorders
Macrocytic megaloblastic anaemias
B12 deficiency
folate deficiency
Nuclear maturation affected
Macrocytic, non-megaloblastic anaemias
Liver disease
Hypothyroidism
Definition of haemolysis
The premature destruction of the mature RBC
Life span of a RBC
120 days
Lab features of haemolysis
• Elevated unconjugated bilirubin
Haem itself is normally degraded to biliverdin, then bilirubin
Bilirubin transported to liver to be conjugated for excretion– but in haemolytic states this system is overloaded
• Elevated lactate dehydrogenase
• Elevated reticulocyte count
suggests a bone marrow response to falling Hb
may also see nucleated red cells in the peripheral blood
• Mildly macrocytic anaemia
Reticulocytes are slightly larger than normal RBCs
What’s intravascular haemolysis and what are the lab features?
Haemoglobin released directly into the bloodstream binds to Hb-binding protein haptoglobin
This system rapidly saturated -> free haemoglobin found in the blood
Hence in intravascular haemolysis: • Low serum haptoglobin levels • Haemoglobinaemia • Haemoglobinuria • Haemosiderinuria
What’s haemosiderinuria?
Hemosiderinuria (syn. haemosiderinuria), “brown urine”, occurs with chronic intravascular hemolysis, in which hemoglobin is released from RBCs into the bloodstream in excess of the binding capacity of haptoglobin. (Haptoglobin binds circulating hemoglobin and reduces renal excretion of hemoglobin, preventing tubular injury.) The excess hemoglobin is filtered by the kidney and reabsorbed in the proximal convoluted tubule, where the iron portion is removed and stored in ferritin or hemosiderin. The tubule cells of the proximal tubule slough off with the hemosiderin and are excreted into the urine, producing a “brownish” color. It is usually seen 3-4 days after the onset of hemolytic conditions.
