Haematology Flashcards
What percentage of blood is plasma and what does this consist of?
55%
Plasma proteins–> e.g. albumin and carrier proteins, coagulation factors (e.g. fibrinogen) and immunoglobulins
Water
What percentage of blood is cells?
45%
RBC + Leukocytes + Platelets
What is serum and what does it contain?
Blood plasma without the clotting factors.
Contains:
Glucose
Electrolytes (sodium and potassium)
Proteins (e.g. immunoglobulins and hormones)
Where do blood cells develop?
Bone marrow
Where is the majority of bone marrow found?
Pelvis, vertebrae, ribs, sternum
What can a pluripotent haematopoietic stem cell differentiate into?
Myeloid stem cell
Lymphoid stem cell
Dendritic cell
What can myeloid stem cells differentiate into?
Megakaryocytes
Erythrocytes
Myeloblasts
What do Megakaryocites produce?
Platelets
What do RBC’s develop from?
Reticulocytes that come from myeloid stem cells.
What is the life span of a:
- platelet?
- RBC?
- 10 days
2. 120 days
What is the role of platelets?
To aggregate (clump together) and plug gaps where blood clots need to form.
What can myeloblasts differentiate into?
Basophil Neutrophil Eosinophil Monocyte Mast cells
What do monocytes differentiate into?
Macrophages
What can lymphoid stem cells differentiate into?
B lymphocytes
T lymphocytes
Natural killer cells
What do B lymphocytes differentiate into?
Plasma cells
Memory B cells
What do T lymphocytes differentiate into?
CD4 cells (T helper cells) CD8 cells (cytotoxic T cells) Natural killer cells
Where do B lymphocytes mature?
Bone marrow
Where to T lymphocytes mature?
Thymus gland
What are reticulocytes?
Immature red blood cells that are slightly larger than standard erythrocytes and still have RNA material in them which has a reticular (mesh-like) appearance.
What is the normal percentage of reticulocytes in the blood and why may it increase?
1% of RBC
Percentage goes up when there is a rapid turnover of RBC’s such as in haemolytic anaemia.
What is anaemia?
Low level of haemoglobin in the blood.
A result of disease-not a disease itself
What is haemoglobin?
A protein found in RBC’s, responsible for picking up oxygen in the lungs and transporting it to the cells of the body.
What should you measure to see if a patient has anaemia?
Haemoglobin levels
Mean cell volume (MCV)
What is the mean cell volume?
The size of their red blood cells
What is the normal haemoglobin and MCV levels in women?
Haemoglobin= 120-165 g/L MCV= 80-100 femtolitres
What is the normal haemoglobin and MCV levels in men?
Haemoglobin= 130-180 g/L MCV= 80-100 femtolitres
What are the 3 types of anaemia (based on size)?
Microcytic
Normocytic
Macrocytic
What is microcytic anaemia?
Low MCV anaemia indicating small RBC’s
What is normocytic anaemia?
Normal MCV indicating normal sized RBCs
What is macrocytic anaemia?
Large MCV indicating large RBC’s
What are the causes of microcytic anaemia?
TAILS: Thalassaemia Anaemia of chronic disease Iron deficiency anaemia Lead poisoning Siderobastic anaemia
What are the main causes of normocytic anaemia?
Acute blood loss Anaemia of chronic disease Aplastic anaemia Haemolytic anaemia Hypothyroidism
What are the two main causes of macrocytic anaemia?
Megaloblastic anaemia
Normoblastic anaemia
What is megaloblastic anaemia?
The result of impaired DNA synthesis preventing the cell from dividing normally. Instead it keeps growing into a larger abnormal cells.
What is the cause of megaloblastic (macrocytic) anaemia?
Vitamin deficiency:
B12 deficiency
Folate deficiency
What are the causes of normoblastic macrocytic anaemia?
Alcohol Reticulocytosis Hypothyroidism Liver disease Drugs (e.g. Azathioprine)
What are the main generic symptoms of anaemia?
Tiredness Shortness of breath Headaches Dizziness Palpitations Worsening of other conditions (e.g. angina, heart failure, PVD)
What are the symptoms specific to iron deficiency anaemia?
Pica
Hair loss
What is pica?
Dietary cravings for abnormal things such as dirt
What are the generic signs of anaemia?
Pale skin
Conjunctival pallor
Tachycardia
Raised respiratory rate
What signs are specific to iron deficiency anaemia?
Koilonychia (spoon shaped nails)
Angular chelitis (red, swollen patches in corners of mouth)
Atrophic glossitis (smooth tongue)
Brittle hair and nails
What are the initial investigations into anaemia?
Haemoglobin MCV B12 Folate Ferritin Blood film
What further investigations could be done to diagnose anaemia?
Oesophago-gastroduodenoscopy (OGD) / colonoscopy to investigate cause of unexplained iron deficiency anaemia.
Bone marrow biopsy if cause unclear/
Under what circumstances may a patient become iron deficient?
Insufficient dietary iron
Iron requirements increase (e.g. pregnancy)
Iron being lost (e.g. slow bleeding in colon cancer)
Inadequate iron absorption
Where is the majority of iron absorbed?
Duodenum and jejenum
How is absorbed iron kept in the soluble ferrous (Fe2+) form?
Due to acid in the stomach
What happens when the acid levels drop?
Ferrous iron changes to the insoluble ferric (Fe3+) form
How do medications such as proton pump inhibitors interfere with iron absorption?
Reduce the stomach acid, meaning it stays in the soluble ferrous form for less time
What can cause inadequate iron absorption?
Medications such as proton pump inhibitors
Conditions that cause inflammation of the duodenum/ jejunum (e.g. Coeliac or Crohn’s disease)
What are the most common causes of iron deficiency anaemia?
- Blood loss –> most common cause in adults
- Dietary insufficiency–> most common cause in growing children
- Poor iron absorption
- Increased requirements during pregnancy
What are the most common causes of iron deficiency anaemia due to blood loss?
Monorrhagia (heavy period) Loss from the GI tract: - Gi tract cancer - Oesophagitis -Gastritis -IBD
How does iron travel around the blood?
As ferric ions (Fe3+) bound to transferrin (carrier protein)
What is total iron binding capacity (TIBC)?
The total space on the transferrin molecule for iron to bind.
What is the transferrin saturation?
The proportion of transferring molecules that are bound to iron/
How is the transferrin saturation calculated?
Serum iron/ Total iron binding capacity
What form does iron take when it is deposited and stored in cells?
Ferritin (Fe2+)
What causes raised blood ferritin?
Extra ferritin is released from cells in inflammation (E.g. infection or cancer)
What does low blood ferritin suggest?
Iron deficiency
Why is serum iron not a very useful measure?
It varies significantly throughout the day. (e.g. in the morning and after meals)
What happens to TIBC/ transferrin levels in iron deficiency?
The levels increase
What measurement gives the best indication of the total iron in the body?
Transferrin
What is the normal transferrin level in adults?
30%
Normal range= 15-50%
What blood tests are used to diagnose iron deficienct anaemia/ iron overload?
Serum ferritin
Serum iron
Total iron binding capacity
Transferrin saturation
What is the normal range of serum ferritin?
41-400 ug/L
What is the normal range of serum iron?
12-30 μmol/L
What is the normal range of TIBC?
45-80 μmol/L
What factors can give the impression of iron overload?
Iron supplementation
Acute liver damage (lots of iron is stored in the liver)
What are the 3 main methods of management for iron deficient anaemia?
- Blood transfusion
- Iron infusion
- Oral iron
What are the benefits/ risks of using a blood transfusion to treat iron deficiency anaemia?
Immediately corrects the anaemia and is very quick.
Does not treat underlying iron deficiency and carries risks.
What are the benefits/ risks of using an iron infusion to treat iron deficiency anaemia?
Very quickly corrects the iron deficiency
Small risk of anaphylaxis and should be avoided during sepsis
What is given as oral iron to treat iron deficiency anaemia and how much?
Ferrous sulfate 200mg three times a day
What are the benefits/ risks of oral iron to treat iron deficiency anaemia?
Least invasive.
Slowly corrects the deficiency.
Causes constipation and black coloured stools.
By how much could you expect haemoglobin to rise when correcting iron deficiency anaemia?
10 grams/ litre per week
What is pernicious anaemia?
An autoimmune condition where antibodies form against the parietal cells or intrinsic factor, preventing the absorption of B12 and causing B12 deficiency anaemia
What are the causes of B12 deficiency anaemia?
caused by insufficient dietary intake or by pernicious anaemia
Where in the body is B12 absorbed and what does it need in order to be absorbed?
Ileum
Needs intrinsic factor produced by the parietal cells of the stomach.
What are the main symptoms caused by B12 deficiency?
Neurological symptoms:
- Peripheral neuropathy–> numbness or paraesthesia (pins and needles)
- Loss of proprioception/ vibration sense
- Visual changes
- Mood/ cognitive changes
How is pernicious anaemia diagnosed?
Testing for autoantibodies:
Intrinsic factor antibody
Gastric parietal cell antibody
How can B12 dietary deficiency be treated?
Oral replacement (Cyanocobalamin)
Why can oral B12 replacement not be used to treat pernicious anaemia?
Because the problem is with absorption not intake.
How can pernicious anaemia be treated?
1mg of intramuscular hydroxycobalamin (B12) 3 times weekly for 2 weeks, then every 3 months.
What is haemolytic anaemia?
Anaemia caused by destruction of red blood cells (haemolysis)
What inherited conditions cause haemolytic anaemia and how?
Cause RBC’s to be more fragile and break down faster than normal:
- Hereditary Spherocytosis
- Hereditary Elliptocytosis
- Thalassaemia
- Sickle Cell Anaemia
- G6PD Deficiency
What acquired conditions cause haemolytic anaemia and how?
Lead to increased breakdown of RBC’s:
- Autoimmune haemolytic anaemia
- Alloimmune haemolytic anaemia (transfusions reactions and haemolytic disease of newborn)
- Paroxysmal nocturnal haemoglobinuria
- Microangiopathic haemolytic anaemia
- Prosthetic valve related haemolysis
What does an abnormal rate of RBC destruction cause?
Anaemia
Splenomegaly–> Spleen becomes filled with destroyed RBCs
Jaundice–> Bilirubin is released during the destruction
What investigations can be done to diagnose haemolytic anaemia?
Full blood count
Blood film–> Shows schistocytes (fragments of RBC’s)
Direct Coombs test (shows autoimmune causes)
What is hereditary spherocytosis?
The most common inherited haemolytic anaemia.
Autosomal dominant condition that causes sphere shaped RBCs that are fragile and break down easily when passing through the spleen.
How is hereditary spherocytosis haemolytic anaemia treated?
With folate supplementation and splenectomy
What is hereditary elliptocytosis?
Same as hereditary spherocytosis except RBCs are ellipse shaped instead of spheres.
What is G6PD Deficiency?
Type of haemolytic anaemia caused by a defect in the RBC enzyme G6PD.
What are the two types of Autoimmune Haemolytic Anaemia (AIHA)?
-Warm type
-Cold type
Based on the temperatures at which the auto-antibodies function to cause destruction of RBCs
What is Alloimmune Haemolytic Anaemia?
When there are foreign RBCs or antibodies circulating in the patients blood causing an immune reaction that destroys them.
What causes Alloimmune Haemolytic Anaemia?
Blood transfusion reactions
Haemolytic disease of the newborn
What is Paroxysmal Nocturnal Haemoglobinuria?
Rare condition that occurs when a specific genetic mutation in the haematopoeitic stem cells in the bone marrow results in a loss of proteins on the surface of RBCs that inhibit the complement cascade.. This results in its activation and therefore the destruction of RBCs
What is Microangiopathic Haemolytic Anaemia (MAHA)?
Where the small blood vessels have structural abnormalities that cause haemolysis of the blood cells travelling through them. Usually secondary to an underlying condition
What is Prosthetic Valve Haemolysis?
Haemolytic anaemia caused by turbulence around the valve and collision of red blood cells with the implanted valve. ( Valve churns up the cells and they break down.)
Where in the body is folate absorbed and what does it do?
Absorbed in the jejunum.
Essential for DNA synthesis and RBC formation.
What happens if the body does not have enough folic acid?
The body makes abnormally large RBCs that don’t work properly and there is decreased RBC production in the bone marrow.
What are the main causes of folate deficiency?
Poor folate diet
Malabsorption
Pregnancy
Anti-folate drugs (e.g. mehtotrexate)
What foods are high in folat?
Green vegetables
How can you differentiate B12 and folate deficiency anaemia based on symtpoms?
Unlike B12, there is no neuropathy
What investigations can be done to diagnose folate deficiency anaemia?
FBC
Blood film - show macrocytic anaemia
Serum and erythrocyte folate levels
How is folate deficiency anaemia treated?
Treat underlying cause
Folic acid supplementation (particularly consider during pregnancy)
What is the structure of haemoglobin?
2 alpha and 2 beta-globin chains
What is thalassaemia?
Anaemia caused by an autosomal recessive genetic defect in the protein chains that make up haemoglobin.
What causes alpha thalassaemia?
Genetic defects in alpha-globin chains
What causes beta thalassamia?
Genetic defects in beta-globin chains
What happens to RBCs in thalassaemia?
They are more fragile and break down more easily
What happens to the spleen in thalassaemia?
The spleen collects all the destroyed RBCs and swells, causing splenomegaly
What happens to the bone marrow in thalassaemia?
It expands to produce extra red blood cells for the chronic anaemia.
What does bone marrow expansion in thalassaemia cause?
Susceptibility to fractures and prominent features such as a pronounced forehead and malar eminences
What are the potential signs and symptoms of thalassaemia?
Microcytic anaemia Fatigue Pallor Jaundice Gallstones Splenomegaly Poor growth and development Pronounced forehead/ cheekbones
How is thalassaemia diagnosed?
Full blood count–> Shows microcytic anaemia
Haemoglobin electrophoresis–> diagnoses globin abnormalities
DNA testing–> Looks for genetic abnormalities
(Pregnant women offered screening)
Why is important to monitor serum ferritin levels in thalassaemia?
Iron overload can occur
Why does iron overload occur in thalassaemia?
As a result of faulty creation of blood cells, recurrent transfusions and increased absorption of iron in response to anaemia.
What are the effects of iron overload?
Fatigue Liver cirrhosis Infertility and impotence Heart failure Arthritis Diabetes Osteoporosis/ joint pain
How is iron overload managed?
Limit transfusions
Iron chelation
What chromosome contains the gene that codes for alpha-globin chains?
Chromosome 16
What chromosome contains the gene that codes for beta-globin chains?
Chromosome 11
How is alpha-thalassaemia managed?
Monitor full blood count Monitor complications Blood transfusions Splenectomy Bone marrow transplant