Haematology - Anaemia, red cell metabolism and transfusion Flashcards
Amount of iron in avg man
4g total
30-45% less in avg woman
What % of iron is stored as Hb
65%
What % of iron is stored as ferritin
20-30%
What is iron stored as excluding Hb and ferritin
Myoglobin
Catalase
Various enzymes
What is iron status regulated by
Absorption
Iron requirements for men and women
Male: 0.5 - 1.0 mg/d
Menstruating female: +0.5 - 1.0mg/d
Pregannacy: +1 - 2mg/d
Growing children: +0.6 - 1.0mg/d
Key players in iron metabolism
DMT 1 Ferritin Transferrrin and transferrin receptors Haemosiderin Ferroportin Hepcidin HFE
Function of DMT 1
Take up Fe2+ from gut into gut wall
When is DMT1 upregulated
Fe deficiency
What is ferritin
Intracellular storage form of iron in the liver
What is ferritin upregulated by
Fe excess
Infl
Role of transferrin
Carries iron around body to transferrin receptors allowing uptake into cells
When is transferrin upregulated
Fe deficiency
Role of ferroportin
Transfer iron for enterocyte into plasma
Opposite to DMT - 1
Haemosiderin
Partial degradation of haemoferritin
Role of hepicidin
Acute phase protein - feedback signal
Controls absorption by binding to ferroportin
Affected in anaemia of c/c disease
Can we actively excrete iron
No
Only passive loss through gut, skin, faeces
Haematinics
What is needed for blood cell formation
Iron - incorporated into haem
AA - make globin chain
Bone marrow blasts - DNA synthesis forms dividing cells to package the O2
Anaemia of c/c disease and hepcidin
C/c disease causes release of IL6 which upregulates hepcidin
Hepcidin is a competitive inhibitor of iron on ferroportin —> decreased uptake of Fe
Factors increasing the absorption of iron
Increased Fe2+ and haem iron Acids and ascorbate in diet Pregnancy Solubilising agents - sugars, AA Increased erythropoiesis Haemochromatosis Increased DMT-1 and ferroportin
Hameochromatosis
Genetic disorder causing body to absorb excessive amount of iron from diet
Iron accumulates over time and causes damage to several organs incl liver
Factors decreasing the absorption of Fe
Increased Fe3+ and non-organic iron Alkali Phytate (tea) and phosphates Tetracycline High iron diet Infections - hepcidin High body iron stores
Ix and mx of IDA algorithm
Confirm IDA
Determine cause
Treat anaemia
Treat underlying cause
IDA
Iron deficiency Anaemia
Microytic anaemias
Thalassaemia trait Anaemia of c/c disease IDA Lead poisoning Sideroblastic anaemia
Labs for IDA
Low MCV
Low serum Fe
Low ferritin
Increased transferrin
Labs of ACD
Low MCV
Low serum Fe
Low transferrin
Labs for thalassaemia
Low MCV
Sideroblastic anaemia
Problem of haem ring
Labs for sideroblastic anaemia
Low MCV
Newer metrics for measuring anaemia
Ret-Hb
% of hypochromic red cells
Measuring functional iron delivery to the bone marrow
Using Ret-Hb to measure anaemia
Reticulocyte-Hb
Low is abnormal
Using % of hypochromic red cells to measure anaemia
Low is abnormal
Measuring functional iron delivery to the bone marrow to measure anaemia
Shorter term changes than Hb or MCV
Abnormal in IDA, ACD and thalassaemia
Causes of iron deficiency
Inadequate diet
Increased requirements
Malabsorption
Blood loss
Examples of increased requirements causing iron deficiency
Pregnancy
Growth
Examples of blood loss causing iron deficiency
Menstrual
GI
Urinary
Lung
Determining cause of IDA
Hx and examination
In UK, dietary deficiency alone is unusual - take diet hx
Menstrual hx - duration, clots, tampons, flooding
GI ix
Othe rcxauses usually obvious - pulm haemorrhage, PMH, urinary hameosiderin
Who gets GI ix for IDA
All men and all post-menopausal women
Symptomatic women
Women 45+ (or 50) check Fhx of colon cancer
GI ix for IDA
Hx Faecal Hb - FIT Tissue transglutaminase antibody (tTG) Image upper and lower GI tracts The above are usually sufficient, if not test stool for parasites
What is important in GI hx for IDA
Drugs - NSAIDs, aspirin, bisphophonates
Imaging upper and lower GI tract for IDA ix
Gastroscopy (duodenal bx) and colonoscopy
Gastroscopy plus CT colonography
GI causes of IDA
Hookworm infections Coeliac disease Crohn's disease Gatritis/ oesphagitis Peptic ulceration Gastrectomy Colon cancer - esp R sided Large polyps Haemorrhoids Diverticular bleeding
Iron replacement drug therapy
Oral ferrous sulphate for 3/12 post Hb-normalisation - 60mg Fe/ 200mg
Ferrous gluconate - 37mg/ 300mg
Sodium ironedetate - 27.5mg/ 5ml
Feric maltose - probably better tolerated (20mg)
What should be avoided in iron replacement therapy
Slow-release preparations
Parenteral iron for IDA
Rarely required
Modern total dose replenishment in 1-2 doses of ferric caboxymaltose/ derisomaltose
Benefits of parenteral iron
Hb responds equivalent
Replensishes stores faster
May be able to overcome some ACD
Low risk of allergic reactions, hypophosphataemia
When should parenteral iron for IDA be considered
If absorption is impaired
When do you switch to parental iron if oral fails
Relatively early (2/52 to 4/52)
What is folic acid synthesised by
Bacteria
Where is folic acid found
Green vegetable, offal
What is folic acid biologically active as
Polyglutamates
What is required for biological activity of folic acid
B12
Store of folic acid vs vit B12
Relatively small store vs large store
What is vit B12 synthesised by
Microorganisms, not by humans
Kay players in B12 metabolism
R binders Gasttric parietal cell Gastric acid Intrinsic factor * Pancreatic secretion Ileal receptor Transcobalamin- I/ II/ III
Which cells are affected by B12 and folate deficiency
All cells
Rapidly dividing cells most vulnerable e.g. bone marrow precursors, gut epithelium
Spp symptoms of B12 deficiency
Neuropathy and optic atrophy
Ix and mx of megaloblastic anaemia algorithm
Confirm haematological dx
Provide replacement therapy
Determine underlying cause
Clinically significant B12 deficiency can occur w/ out haematological effects
Confirming haematological dx of megaloblastic anaemia
Blod film
B12 and red cell folate levels
Condiser other causes of macrocytosis
Bone marrow
Can clinically significant B12 deficiency occur w/ out haematological effects
Yes
What can microcytic anaemia be divided into
Megaloblastic and non-megaloblastic
Causes of megaloblastic microcytic anaemia
B12/ folate deficiency or combined
Abnormal folate metabolism - MTX
Abnormal DNA synthesis
Myelodysplasia
Abnormal DNA synthesis causing megaloblastic macrocytic anaemia
Orotic acuduria
Azathioprine
Zidovudine
Orotic aciduria
Disease caused by enzyme deficiency resulting in decreased ability to synthesise pyrimidines
Causes of non-megaloblastic macrocytic anaemia
Pregnancy Liver disease Alcoholism Retiuclocytosis Hypothyroidism Drugs Marrow infiltration Sideroblastic anaemia Cold agglutinins
B12 replacement therapy
Parenteral hydroxycobalamin
3 monthly replacements
Oral replacement if absorption intact
When is B12 given as prophylaxis
After total gastrectomy or ileal resection
Folate replacement therapy
Oral folic acid 4/12 or continuously
Folicinic acid for DHF-reductase inhibition - MTX
Why is folate given after B12 in combined deficiency
Initial folate may exacerbate neuropathy
When is folate given as prophylaxis
Pregnancy and preconception - neural tube defects normal risk vs high risk
Haemolysis
MTX therapy
Causes of folate deficiency
Diet Increased utilisation Malabsorption Urinary loss Drugs
Diet causing folate deficiency
Anorexia
Children
Elderly
Alcoholics
Increased utilisation causing folate deficiency
Physiological - pregnancy, growth
Pathological - haemolytic, cancers, infl
Malabsorption causing folate deficiency
Diffuse small bowel diseases
Urinary loss causing folate deficiency
Haemodialysis
Drugs causing folate deficiency
Phenytoin - anti-seizure
Primidone - anti-epileptic
SSZ & related drugs
MTX
Causes of B12 deficiency
Diet Gastric disease Ileal disease Infections Pancreatic disease Transcobalamin-II deficiency B12 destruction
Diet causing B12 deficiency
Vegan
Gastric disease casing B12 deficiency
Autoimmune gastritis
Major gastrectomy
Ileal disease causing B12 deficiency
Resection
Infl
Infections causing B12 deficiency
Small bowel bacterial overgrowth Fish tapeworm (D latum)
B12 destruction causing B12 deficiency
Nitrous oxide
B12 absorption tests
57/58Co labelled B12
+/- intrinsic factor
Urinary excretion or whole body counting
Ix for causes of B12 deficiency
Dietary hx Autoantibodies - anti-parietal cells, anti-intrinsic factor (pernicious anaemia) B12 absorption tests Small bowel FT and bx Gastric bx Gastric and pancreatic function tests
Ix for causes of folate deficiency
Dietary hx
Autoantibodies - anti-gliadin, anti-0endomysela
Duodenal bx
Consider systemic diseases
Nutrients essential for normal RBC formation
Iron Folate Vit B12 Vit B6 Vit C Vit E Copper Protein
Out of the nutrients essential for normal RBC function, which are we most likely to have deficiencies in
Iron
Folate
Vit B12
Symptoms seen in anaemia
V non-spp
Tiredness Weakness Pale skin Tachycardia SOB Chest pain Dizziness Numbness or coldness in extremities FTT and growth retardation in children
Epidemiology of IDA
Most widespread nutritional problem WW
Caused debilitated health of 500 million women, >60,000 deaths during childbirth
Increased morbidity and mortality, decreased productivity
Most vulnerable groups of IDA
Women of child-bearing age - menstrual blood loss and pregnancies
Children - increased requirements for Fe to meet growth (muscles, tissues, menarche)
What does iron bioavilabity reopen on
Physiological factors
Dietary factors
Risk factors that can lead to IDA
Long-term use of PPIs
Blood loss
Pregnancy
H. pylori infection
Dietary factors that explain ID in industrialised countries
Low bioavailability
Sedentary lifestyle
Lower micronutrient density - processed foods
Dietary sources of B12
Products of animal origin e.g. meat (esp liver), poultry, fish, milk, eggs
Fortified breakfast cereals
Fermented foods e.g. sauerkraut
Is folic acid naturally present in food
No - it is used to fortify foods
Folate vs folic acid absorption
Folic acid is highly bioavailable (85%) and folate are less absorbed (50%) and partially destroyed on cooking
Alcohol consumption in creases requirements
Dietary sources of folate
Liver Yeast extract Green, leafy vegetables Legumes (beans, lentils) Orange juice Fortified cereals
Vulnerable group for nutritional anaemias
Infants and children (Fe) Vegans (Fe and B12) Pregnant women (Fe and folate) Elderly (all 3) Low income Ethnic minorities
Why is iron deficiency v rare in infants <4-6/12
Foetal Hb has sufficient stores
Late (i.e 2. mins delay) cord clamping is important
High efficiency of absorption from breast milk; cows filk formulas are fortified
Why is iron deficiency in infants more common after 6/12
Inappropriate weaning
Poor wt gain
Frequent infections
Developmental delay
Behavioural disorders
Iron and B12 deficiency in children
Prolonged bottle/ breast feeding may lead to ID
If weaning foods have a low Fe content –> ID
Vein children may require Vit B12 supplements
How do physiological adaptations in pregnancy affect
iron absorption
Fe absorption increases by ~50% in 2nd trimester and 4x in 3rd trimester
Despite this, the iron deficit is 400-500mg
Why are pregnant women at a higher risk of folate deficiency
Higher physiological requirements (DNA synthesis and other 1-C transfer reactions)
What is the significance of women w/ MTHFR mutation and pregnancy
They require addn folate to reduce their increased risk of NTDs
Anaemia in the elderly
Higher risk of nutritional deficiencies Impaired absorption Poor quality meals in institutions Lower socio-economic status Mental problems
Preventive action of anaemia in the elderly
Increase the micronutrient density of the diet
Dietary assessment for anaemia
Growth in children (percentile charts)
Detailed diet hx - meal patterns and food group
Changes in appetite and food intake
Medical hx
Nice pre-conception advice and nutritional deficiencies
Assess couple’s risk of NTD
Thos at high risk should take folic acid 5mg daily until 12th week and those at normal risk 400micrograms
Lymph nodes in the head & neck
Submental Sublingual Submandibular Parotid Anterior cervical chain Posterior superficial cervical chain Supraclavicular Occiptal Postauricular
Border of axillary lymph nodes
Medial wall (chest wall)
Lateral (humerus)
Anterior (pectoralis major)
Posterior (lat dorsi)
Groups in inguinal lymph nodes/ groin nodes
Horizontal
Vertical
Infectious causes of lymphadenopathy
Viral/ bacteria/ parasitic (generalised)
In areas drained by lymph nodes or involving lymph nodes
Malignant causes of lymphadenopathy
Haematological - lymphoma, CLL, ALL
Non-haematological - metastatic
Miscellaneous causes of lymphadenopathy
SLE
Sarcoidosis
Drugs
How many segments is the abdomen divided into
9
Segments of the abdomen
RH/ LH - Right/ left hypochondriac E - epigastrium RF/ LF - right/ left flank U - umbilical region RIF/ LIF - right/ left iliac fossa SP - suprapubic
How does the liver expand in hepatomegaly
Downwards
Towards RIF
How does the spleen expand in splenomegaly
Diagonally
Towards RIF
Types of causes of splenomegaly
Infection
Infl
Congestion
Infiltration
Infective causes of splenomegaly
EBV
Malaria
Leishmaniasis
TB
Infl causes of splenomegaly
RhA
SLE
Congestive causes of splenomegaly
Cirrhosis (portal HTN)
Haemolysis
Infiltrative causes of splenomegaly
Gaucher's Metastatic cancers Lymphoma CLL Myeloproliferative neoplasms (PV/ MF/ CML)
PV
Polycythemia vera
MF
Myelofibrosis
What do RBCs need to function
Efficient production (synthesis) To be pliable (get through small vessels) Hb on which to carry O2 Ensymes for metabolism Removal of defective cells
Erthryopoiesis
Synthesis of RBC in bone marrow
Erythroblast –> nucleated RBC –> reticulocyte –> mature red cells
Requirements for erythropoiesis
Normal stem cell Normal maturation Healthy bone marrow microenvironment Growth factors Essential components
Growth factors needed ion erythropoiesis
Erythropoietin
GM-CSF
Addn essential components for erythropoiesis
Fe
Vit B12
Folate
AA
What are RBC membrane’s held together by
Proteins - some intrinsic (Band 3 which forms vertical scaffold) and horizontal scaffold formed by spectrin
Hb structure
Tetramer - 2 pairs of globin chains
Haem molecules bound to each globin
Iron within centre of haem
Phases of Hb production
Embryonic
Foetal
Adult
Does embryonic Hb have clinical implications
No
When does disease caused by defect in beta chain manifest
3/12 - 6/12 after birth
What chromosome codes for alpha chain
16
Where are alpha chains in Hb found
In all Hb from foetal to adult
What chromosome codes for beta-like chains in Hb
11
How many more alpha chains do we have compared to beta chains in Hb
2x as many alpha
Beta-like chains in different Hb
Beta in HbA (adult) (2:2 ratio for alpha)
Gamma in HbF (foetal)
Delta in HbA2 - v low levels from week 30 gestation
Why do RBC need enzymes for metabolism
Mature RBC has no nucleus or mitochondria so require enzymes for response to oxidative stress e.g. G6PD and ATP production
What happens if there are defects in the enzymes RBCs use for metabolism
Portion of RBCs that are susceptible to oxidative stress and die early due to ATP depletion
Normal RBC lifespan
120 days
How are old RBC removed
Macrophages - phagocytosis
Where are macrophages that remove old RBCs found
Spleen
Liver
Marrow - prevent damaged cells from entering circulation (protective mechanism)
What is anaemia
Reduced g of Hb/L blood below the age/ sex adjusted normal range q
What may anaemia occur as a result of
Too few RBCs
Too little Hb
An abnormally low haematocrit
Haematocrit
Ratio of RBC:plasma - aka packed cell volume
Reduced if increased plasma or decreased RBC
A/c vs c/c symptoms of anaemia
A/c - symtoms more marked
C/c - symptoms less severe; time for body to compensate
Less common symptoms of anaemia
Muscle cramps
Angina/ heart failure - anaemia exacerbates these condns
Signs of anaemia
Pallor - look in conjuctiva in darker skinned individuals
Tachypnoea
Tachycardia
Hypotension
Causes of normocytic anaemia
ACD A/c blood loss A/c renal failure Bone marrow disorders Mixed B12/ folate and iron deficiency
How can we classify causes of anaemia aside from MCV
Reduced RBC production
Increased RBC destruction (haemolysis) or loss
Causes of reduced RBC production leading to anaemia
Defective stem cells Defective maturation Unhealthy microenvironment Absence of stimulation by growth factors Lack of components for RBC formation
Reduced RBC production as a result of defective stem cells
Inherited e.g. Diamond-Blackfan anaemia (rare)
Acquired - drugs, infections, immune (aplastic anaemia)
Aplastic anaemia
Bone marrow does not produce new blood cells
Empty bone marrow on bx
Defective maturation leading to reduced RBC production
Lack of nutrients e.g B12 deficiency
Myelodysplasia
Unhealthy microenvironment leading to RBC production
Damaged e.g. radiation, infections
Lack fo space due to fibrosis, haematological malignancy, non-haematological malignancy
Reduced RBC product as a result of absence of stimulation by growth factors
Decreased erythropoietin - renal failure