Haematology Flashcards
Erythrocyte life cycle
Maturation process
What happens to old RBCs?
What are the breakdown components and what happens to them?
Bone marrow: Stem cell (myeloid progenitor cell) -\> proerythroblast -\> erythroblast -\> reticulocyte: spends 3 days in BM then enters blood stream
Blood stream
Retic matures into erythrocyte over 24-48 hrs -> Erythrocyte: circulates in blood stream over about 120 days
Old/abnormal erythrocytes (120 days) -> travel to spleen/liver -> broken down by macrophages and monocytes into components globin and heme
Heme -> bilirubin and iron
Globin -> amino acids
- Amino acids enter back into circulation and travel back to bone marrow to be involved in erythropoeisis
- Iron travels back to blood stream attached to transferrin via liver to be involved in heme production
- Bilirubin travels to liver to be excreted into intestine via bile ducts -> excreted via faeces or urine or reabsorbed
How does O2 circulate in blood
O2 travels around blood via RBC (bound to Hb within RBC)
Configuration of deoxyhaemoglobin
How does this change with O2 binds
Deoxy (no O2 bound) = Tight structure
-> has 2,3 DPG bound with DECR affinity for O2
When 1 O2 molecule binds, it becomes more relaxed which further increases its affinity/ability for O2 to bind (can bind max 4 O2 molecules)
What factors affect affinity of O2 for Hb (shift in oxyhaemoglobin dissocation curve)
pH
pCO2
altitude
temperate
2,3 DPG
methaemoglobin
HbF (foetal)
What shape is the Hb dissociation curve?
At what point in the Hb-dissociation curve does Hb affinity for O2 decrease
Sigmoidal shape
X-axis pO2 of 50mmHg corresponds to y axis % Hb saturation of 90%
- above this O2 remains tightly bound (plateau)
- below this O2 is easily removed from Hb (exponential decr)
What causes a RIGHT shift in oxyhaemoglobin dissociation curve
Right = Reduced affinity of Hb for O2 -> O2 released into tissues
Occurs in tissues normally (placenta, muscle cells)
Other factors
- Incr CO2
- Low pH (acidosis/incr H+)
- Incr temp/fever
- Incr 2,3 DPG (created during glycolysis, reduces affinity for O2)
***To remember: an exercising muscle is hot, hypercarbic, acidic, glycolysis active, and benefits from increased unloading of O2 ie lower affinity = right shift***
What causes a LEFT shift in oxyhaemoglobin dissociation curve
Higher affinity of Hb for O2 -> O2 BOUND more tightly to Hb (occurs in lungs)
Other factors
- Decr CO2
- High pH (alkalosis/low H+)
- Decr temp/hypothermia
- Decr DPG
- Abnormal Hb (sickled, methaemoglobin)
***To remember: an exercising muscle is hot, hypercarbic, acidic, glycolysis active, and benefits from increased unloading of O2 ie lower affinity = right shift***
Effect of fetal Hb on O2 dissociation curve
Why does this occur?
How long does this persist?
From 10-12 weeks in utero
Persists until 6 mo of life
Shift of Hb dissociation curve to the LEFT -> greater affinity for O2 (Can bind more O2 at lower pO2)
So can as has to obtain O2 from mother’s blood stream
This is due to decreased affinity of fetal Hb to 2,3 diphosphoglycerate (DPG), so O2 can bind with higher affinity
Persists to ~6mo of life
Difference in structure between fetal and adult HbF
When does the switch occur?
Fetal Hb = alpha2gamma2
- 2x alpha and 2x GAMMA subunits
Adult Hb = alpha2beta2
- 2xalpha and 2 x BETA subunits
Switch from fetal to adult around 3-6mo
Function of 2,3 diphosphoglycerate (DPG)
Binds to adult Hb and decreases its affinity for O2 -> causes RIGHT shift in O2 dissociation curve
(Present in de-oxy form of Hb, TIGHT structure without O2)
What are the various forms of Iron and what are their relative sources?
Which form can be absorbed?
What is the absorption process for iron?
Iron is a avilable in 2 forms
- Ferrous 2+ from animal sources (‘heme iron’) - readily absorbed in SI (so give supplemental iron in this form)
- Ferric 3+ from vegetable sources (‘non-heme iron’) - not absorbed so must be converted to ferrous iron (Fe2+) via VITAMIN C ferrireductase in lumen of duodenum (enterocyte) then absorbed via DMT1 transporter
- Converted back to Ferric form (Fe3+) when absorbed into bloodstream
- Travels in blood bound to transferrin (transporter molecule) to target organs (liver for storage as ferritin and BM to be incorperated into haem)
Apo-transferrin
Vs Transferrin
Transporter of iron
Apo-transferrin - when unbound
Transferrin - when bound to Ferric (Fe 3+) in blood (can carry 2x)
Fate of Fe in bloodstream
75% - to bone marrow for haematopoeisis (Hb, carries O2)
25% - to liver for storage of iron as ferritin (3+)
Transferrin receptor
- where is it located and what does it do?
Present in liver and bone marrow
Enables passage of transferrin (with Fe3+ bound) via endocytosis
Hepcidin
- where is it located/made
- what does it do
Master iron regulator
Produced by liver
Decreases Fe3+ in plasma
- Prevents iron release from cellular storage by blocking ferroportin transporter
- Prevents absorption of Fe in small intestine
Ferroportin
Transporter in liver through which Fe3+ is released from storage (ferritin) into circulation
Hereditary haemochromatosis
What is this caused by?
What does this result in?
Iron storage disorder
Caused by mutation in HFE protein gene
(Autosomal recessive condition)
-> hepcidin will not work to inhibit Fe from intesine or prevent release of Iron from storage in liver->
Results in iron overload and deposition in tissues
Presentation
- Usually presents in middle age
- Bronze discolouration of skin
- Chronic tiredness
- Joint pain
- Memory problems
Hepcidin: what is its role and what factors act to produce/increase the levels of hepcidin
Hepcidin acts to decr [fe3+] in plasma (by reducing dietary absorption and inhibiting release of iron from cellular storage)
Hepcidin levels increase with:
- Expression of HFE protein (made by HFE gene or haemochromatosis gene)
- Incr serum Fe3+ (neg feedback)
- Inflammatory cytokines (is an acute phase reactant)
- Lipopolysaccharides
What is transcobalamin 1 and 2 and what are their roles
Transport proteins for vitamin B12
- Transcobalamin 1 = haptocorrin
- Derived from salivary glands in mouth
- Binds Vitamin B12 and protects it from degradation by stomach acid
- Transcobalamin 2
* Binds vit B12 in serum after it has been absorbed and transports it to target tissues
Absorption of vitamin B12
B12 ingested -> binds to haptocorrin (transcobalamin I) in saliva to protect B12 from degradation by HCl in stomach
- > HCl and intrinsic factor produced by parietal cells in stomach
- Passes into duodenum
- Pancreas produces proteases through pancreatic duct indo duodenum -> release haptocorrin from B12
- > IF binds B12 in duodenum
- IF-B12 complex transported through SI to terminal ileum where IF binds IF-receptor and complex is absorbed and B12 is released into blood
- B12 binds to transcobalamin II and transported to liver and kidneys
- B12 stored in liver
- B12 reabsorbed and excreted through urine (is water soluble)
Role of vitamin B12
Causes of low B12
Ix findings of B12 deficiency
ROLE:
- DNA, RNA synthesis
- RBC production
- Lipid (neuronal myelin sheath) synthesis
- Acts as a cofactor for enzymatic activation for production of
- homocysteine -> methionine
- MMA -> succinyl coA
Causes
- Vegans (in animal products only)
- Impaired absorption:
- Ileal resection
- Coeliac or crohn disease
- Bacterial overgrowth
- Pernicious anaemia (IF factor deficiency)
- Inborn errors of metabolism
Ix
- Macrocytic anaemia with hypersegmented nuclei
- Elevated LDH
- Increased serum homocysteine and urine MMA levels (metabolic precursors)
What does a lack of vitamin B12 lead to in terms of sx
*Mouth, skin and neuropathy*
1) Axonal demyelination -> NEUROPATHIES *specific to B12 def*
- > motor problems/Muscle weakness and unsteady movement
- > numbness tingling
- > developmental delay/regression
- > seizures
2) Anaemia -> fatigue, SOB, pallor, GLOSSITIS, angular stomatitis
3) Mild jaundice, purpura, melanin pigmentation
Pernicious anaemia
- what is it
- what does it result in
Autoimmune disorder, T-cell mediated
Attacks parietal cells
Results in lack of IF production
Prevents absorption of vitamin B12
Leads to vitamin B12 deficiency
Folate
- what is it derived from
- where is it absorbed
- what does it do
- how long do stores last
ie folic acid or Vitamin B9
Derived from diet (green, leafy foods and fortified foods)
Absorbed in jejunum
Precursor for formation of tetrahydrofolate (THF) which acts as a carbon donator and acts as a cofactor for many enzymes involved in nucleic acid and amino acid synthesis (DNA and protein synthesis)
Stores limited to several weeks (deficiency can develop in hospitalised pts)
Causes of deficiency
- malabsorption: coeliac disease, crohn disease
- inadequate dietary intake
- incr physiological demand: prematurity and pregnancy
- incr utilisation: haemolysis, malignancy, inflammatory disease
- liver disease
- anti-folate drugs: MTX, phenytoin, trimethoprim
Affect of methotrexate on folate metabolism
Inhibits metabolism of folate to its active form
- Prevents action of dihydrofolate reductase and thus prevents formation of tetrahydrofolate
(note tetrahydrofolate (THF) which acts as a carbon donator and acts as a cofactor for many enzymes involved in nucleic acid and amino acid synthesis)
Causes of microcytic anaemia
TAILS
Thalassaemia
Anaemia of chronic disease (ESRF)
Iron deficiency
Lead poisoning
Sideroblastic anaemia (XLR) - very rare!!
Someone has a normocytic anaemia
What is the next ix you would look at
What are causes of such
Reticulocyte count; plt and WCC (?pancyopaenia)
High Retics
- Haemolysis
- Bleeding
Low retics = marrow failure
- Pancytopaenic
- Aplastic anaemia
- MDS
- Leukaemia
- Myelofibrosis
- TB
- Amyloidosis, sarcoidosis
- drugs (chemo)
- Non pancytopaenic
- Anaemia of chronic disease
- Renal disease
- Mixed nutritional deficiency (iron+B12)
- TEC
Someone has a macrocytic anaemia
What is the next ix you would look at
What are causes of such
Blood film to differentiate between megaloblastic (large immature RBCs) or non-megaloblastic and presence/absence of hyper-segmented neutrophils
Megaloblastic anaemia
- Vit B12 or folate deficiency
- Inborn errors of metabolism (ex orotic aciduria)
- Drug side-effect (Mtx)
Non-megaloblastic
- Brisk reticulocytosis/haemolysis
- Myelodysplastic syndrome
- Marrow failure: Fanconi and Diamond-Blackfan anaemia
- Congenital dyseryrthropoeitic anaemia
- Osteoporosis
- Hypothyroid
- Liver disease, Alcohol
- Post-splenectomy
Blood markers of haemolytic anaemia
Blood
- Reticulocyte count = elevated
- Unconjugated hyperbilirubinaemia
- Elevated LDH
- Elevated free plasma Hb
- Low or absent haptoglobin (binds free Hb from lysed RBCs and are removed from circulation)
Increased Urinary urobilinogen and faecal stercobilinogen
Causes of aneamia - decr production
- Bone marrow disorders (aplastic anaemia)
- CKD (low erythropoeitin)
- Hypothyroid (TSH helps stimulate erythropoeis)
- Vit B12 deficiency
- Iron deficiency
- Chronic inflammatory disease (decr RBC lifespan and causes iron deficiency)
Causes of haemolysis: Intrinsic/cellular
HEREDITARY
Membrane
- hereditary spherocytosis
- elliptocytosis
Enzyme
- G6PD deficiency
- Pyruvate kinase (PK) deficiency
Haemoglobinopathies
- Sickle cell disease
- thalasseamia
ACQUIRED
Autoimmune
- Warm Ab (SLE, dermatomyositis)
- Cold Ab (CMV, mycoplasma)
Alloimmune
- Transfusion reaction
- Haemolytic disease of newborn
- transplant (BMT, cardiac)
Microangiopathic
- HUS
- TTP
- DIC
- meningococcal septicaemia
Infx: malaria
Systemic disease: renal or liver disease
What causes hereditary spherocytosis
Presentation
Ix findings - FBE, Coombs, diagnostic test
Treatment
- AD Gene mutations (ANK1) cause red blood cells to have an abnormal, spherical shape with decreased flexibility (=spherocytes) .
- Due to misshapen proteins in cytoskeleton (most commonly ankyrin-1; spectrin, band 3)
- The spherocytes are taken out of circulation prematurely and sent to the spleen to be destroyed (hemolysis).
Presentation
- *May be asymptomatic
- Neonatal jaundice
- Splenomegaly
- May have pigment gallstones at early age
- Aplastic or anaemic crises esp w PARVOVIRUS infections
Ix:
- Macrocytic anaemia w reticulocytosis
- Elevated bili and LDH
- NEG Coombs/DAT
- RBC Membrane studies/EMA binding is diagnostic (used to do osmotic fragility)
Treatment
- Folic acid supps
- Transfusions if severe anaemia, poor growth, aplastic crisis, age < 2 years
- Splenectomy if regular transfusions required
- Cholecystectomy if gallstones
Complications of haemolytic anaemia
- Erythroid hyperplasia (esp with thalassaemia)
- medullary spaces expand in skull and long bones at expense of cortical bone -> leads to pathological fractures - Gallstones (due to deposition of calcium bilirubinate)
- iron deficiency (iron loss in urine secondary to breakdown of RBCs)
What is an aplastic crisis?
What is the most common cause of aplastic crisis?
Erythroid marrow failure leading to decr reticulocytes and rapid reduction in Hb and Hct to extremely low levels (within 10-14 days)
Can be life-threatening
Most common cause is parvovirus B19
Causes of extracellular haemolysis
Autoimmune
- Warm ab
- Cold ab
Fragmentation Haemolysis (fragments of RBCs will be found in urine)
- DIC (disseminated intravascular coagulation)
- Haemolytic uraemic syndrome
- Artificial heart valve (shear stress)
- Thrombotic thrombocytopaenic purpura
- Hypersplenism
Plasma factors
- Liver disease
- Infection (malaria)
- Wilson’s disease
What is the role of the direct vs indirect Coombs test
Direct (DAT) - detects Ab or complement bound to RBC surface
- Patients RBCs are added to coombs reagent (which are Ab against human globulin)
- Use to detect autoimmune haemolysis, drug-induced or alloimmune hemolysis (newborn or transfusion reaction)
Indirect - detects Ab in serum (RBCs have been removed)
- Add patient’s plasma to RBCs of known Ag
- Then add Coombs reagent (which are Ab against human globulin)
- Use for cross-matching (pre-transfusion) or pre-natal Ab screen (rhesus)
Agglutination = positive test
(NOTE can be initially negative if haemolysis is very rapid)
Indirect Coombs test
If agglutination occurs with patient’s plasma and with donated RBCs of known AB, A but not to B or O, then what sort of blood can this patient be given if they need a transfusion?
Pt cannot be given A blood (Ab would attack -> haemolysis of RBCs)
But CAN safely be given O and B type blood.
What is the Flow cytometric EMA (eosin-5-maleimide) binding test used to diagnosis due to its high predictive value?
Hereditary spherocytosis
Evans syndrome
Autoimmune Haemolytic anaemia + ITP
Cold autoimmune haemolysis
- Optimal temp for agglutination
- Immune cells involved
- Causes
- presentaiton
- ix
- tx
- Optimal temp for Ab attachment to RBC = 4 C
- IgM mediated -> complement cascade -> C’ mediated intravascular (mostly) and liver destruction of RBCs
Causes:
Idiopathic
Infections
- Mycoplasma pneumoniae (most common cause in kids)
- EBV, CMV infection
Lymphomas
Paroxysmal cold haemoglubinuria
Presentation
- Often occurs 1-2 weeks post febrile illness with dark urine following exposure to cold
- Intravascular haemolytic anaemia
- Haemoglobinuria - dark urine
- ACROCYANOSIS
Ix
- Macrocytic anaemia w reticulocytosis
- Positive Coombs to C3b at 4C
Tx
- Treat cause as able
- Cold avoidance/keep warm
- Rituximab
- Folic acid
- NOTE: splectomy not done, GC less useful
Warm autoimmune haemolysis
- Optimal temp for agglutination
- Immune mediator(s)
- Causes
- presentaiton
- ix
- tx
- Destruction in spleen (extravascular) at temps >= 37C
- IgG mediated
Causes
- Primary (idiopathic - 40-50%)
- Secondary to underlying disease such as
- Lymphoma
- SLE, RhA
- Evans syndrome (assoc immune mediated thrombocytopaenia)
Presentation
- Extravascular haemolytic anaemia
- Splenomegaly
- Evans syndrome = assoc ITP +/- neutropenia
Ix
Macrocytic anaemia w reticulocytosis
DAT positive for IgG at 37C
Spherocytes on blood film (not a feature in Cold AIH)
Tx for severe disease
- Treat cause if possible
- GC (not for Cold AIH)
- > IVIG if refractory to GC
- Immunosuppression
- Folic acid, blood transfusions as necessary
- Splenectomy if poor response to medical mx
Beta thalassaemia
Partial (minor) or complete deficiency in betaglobin chains that make up Hb molecules (present in adult but not fetal Hb) with excess alpha chains
Due to POINT MUTATION in beta globin gene on chromosome 11
Minor (trait) - asymptomatic (often picked up incidentally with mild microcytic hypochromic anaemia)
- *Major -** symptoms develop around ~4-6mo (when switch from gamma to beta chain normally occurs). NO HbA.
- > haemolytic anaemia and transfusion dependence
- Hepatosplenomegaly due to haemolysis and extramedullary haemopoeisis
- Thalassaemic facies (frontal bossing nad maxillary hyperplasia)
- Elevated bili, jaundice and gallstones
- Bone deformities and osteoporosis due to extramedullary haematopoeisis
- FTT
- Effects of iron overload from regular blood transfusions (endocrine effects: DI, hyothtyroid, hypoPTH, hypogonadism, GH deficiency, renal disease) and also from hepcidin deficiency (which increases GI iron absorption)
Inheritance of beta thalassaemia
Autosomal recessive
beta 0 = no beta globin produced
beta + = reduced beta globin production
Beta thal Major - 2 x beta 0 mutations - no beta globin chains
- Severe Transfusion dependent disease
- HbF and HbA2, no HbA
Intermitae - 2 beta + (reduced) mutations or beta+/beta0
Minor - 1 beta 0 or + mutation, 1 normal beta gene
- Asymptomatic (often picked up incidentally with mild microcytic hypochromic anaemia)
- Relative excess of alpha chains (elevated HbA2)
Structural variants
- Beta thal/HbE - severe transfusion dependent disease
- Beta thal/HbS - sickle cell disease
Complications of hemochromatosis (iron overload)
-
Liver – cirrhosis, carcinoma
* more common in sickle cell and Diamond blackfan anaemia -
Heart (most common cause of death) – cardiomegaly, arrhythmias, CCF
* more common in beta thal -
Endocrine
- IDDM
- Growth failure
- Delayed puberty
- hypothyroid
- hypoparaythoid
- more common in beta thal
4. osteoporosis and poor growth
Ix
- ferritin (should be less than 1000 to avoid toxic effects; correlates w survival and cardiac effects but correlates poorly w liver effects)
- echo
- endocrine ix
- MRI to look for iron stores
Ix for beta thalassaemia major
Ix
Radiology
- ‘hair on end’ on Skull Xray from expansion of medullary cavities in skull from new bone formation (incr bone marrow activity for production of new retics)
- Hepatosplenomegaly (extramedullary haematopoeisis)
- FBE: microcytic hypo chromic anaemia
- Film: target cells, basophilic stippling, nucleated red cells
- May have normal or elevated serum iron/ferritin
Confirm with Hb electrophoresis
- Elevated HbA2 (alpha2delta2) and HbF (alpha2gamma2) levels
- Decr HbA (alpha2beta2)
Mgmt beta thalassaemia
Minor - no tx
Major and intermedia
- Periodic blood transfusions q4-6wkly
- Hydroxyurea (induces production of HbF which is protective)
- Iron chelating agents (desferrioxamine) as blood transfusions can worsen iron overload (hemochromatosis)
- Folic acid daily
- Vit C daily (incr iron excretion)
- Splenectomy to decr blood requirements (only if >6y)
- HSCT
- Gene therapy
- Hepcidin supplement is a new threapy… (as in thalassaemia is a low hepcidin state)
Alpha thalassaemia
Inheritance
Deficiency in alpha globin chain in Hb (present in both fetal and adult Hb)
- 4x Genes on chromosome 16 (2 from mo, 2 from fa)
- HAve 4 alpha genes, 2 inherted from mo and 2 inherited from father
- alpha0: no alpha globin production at all.
- alpha+: reduced alpha globin production
- 1 or 2 loci of alpha gene deleted (aa/a- or a-/a- or aa/–) = ‘trait/minor’, asymptomatic (hypo chromic microcytic cells +/- mild anaemia)
No MGMT required - 3 alpha genes deleted = a-/– = HbH ( has high O2 affinity, L shift of curve)
Results in unpaired beta globin chains (HbH = beta x 4)
Moderatively severe hemolytic anaemia, splenomegaly
Usually diagnosed late childhood.
Transfusions as needed (sometimes w illnesses, pregnancy) - 4 loci deleted = Bart’s hemoglobin (gammax4 in fetus with NO alpha chains at all)
- > unable to carry O2 = non-viable
- > results in hydrops fetalis/death in utero
- > all postnatal Hb contain alpha chains, so incompatible w life
- > massive hepatosplenomegaly and signifiant morbidity for mo during pregnancy
- > survivors are transfusion dependent
Most accurate test for diagnosing thalassaemia
African/mediterranean/SE asian populations
Antenatally
- CVS or amniocentesis for foetal DNA analysis
- Foetal blood sampling in 2nd trimester via cord blood for Hb electrophoresis
Neonatal diagnosis
- Hb electrophoresis at birth (however may ned to be redone at 6 months due to switch from gamma to beta chairs occurring at 3-6mo)
How does iron overload cause cell damage?
Highly toxic labile iron -> free radical -> lipid peroxidation, DNA modifications, protein damage
i. TGF-β1 -> collagen synthesis -> fibrosis
ii. Organelle damage -> cell death
iii. Resultant organ damage
Sickle cell disease
pathophys/genetics
What is the difference between sickle cell anaemia and sickle cell disease and sickle cell trait?
Affects HbA due to mutation in Hb beta globin gene (HBB gene) resulting in misshapen Hb molecule (sickle) when exposed to low O2 conditions
-> single base pair change (valine instead of glutamic acid)
The sickled cells bock areas of microcirculation resulting in microinfarcts
- SS anaemia = HbS/HbS = Both β-globin alleles have the sickle cell mutation (βs)
- SS disease = Compound heterozygote one β-globin allele includes the sickle cell mutation and the second β-globin allele includes a gene mutation other than the sickle cell mutation ie. HbS/HbC, HbS/β-thalassemia
- SS trait = One allele of the beta globin gene carries the sickle mutation and the other allele is normal, producing haemoglobin SA (HbSA)
Sickle trait
Clinical features
No health problem unless exposed to EXTREME trigger (altitude/hypoxia/dehydration)
Decreases severity of malaria (plasmodium falciparum)
-> heterozygote advantage in ppl of African/mediterranean/indian/SE asian descent
Haematuria is commonest symptom
What triggers sickling and what does this lead to?
Triggers
- hypoxia
- dehydration
- acidosis
- Changes shape when de-oxygenated -> crescent shape (sickled)
- Sickled erythrocytes are rigid and obstruct small blood vessels (VOC)
- Leads to premature destruction/hemolysis of RBCs
-> Vaso-occlusion and micro infarcts
Howell Jolly Bodies are a path feature of what condition?
Sickle cell anaemia (have functional asplenia)
Splenic dysfunction/asplenism
Inx for diagnosis of sickle cell
Blood smear (sickled cell, target cells, howell jolly bodies, polychromasia from retics) Hb electrophoresis (HbS present) Sickledex test (HbS sickles when deoxygenated with dithionite and Na2HPO4) Macrocytic anaemia, reticulocytes high
Mx of sickle cell disease
General
- Avoid triggers (hypoxia, dehydration, acidosis)
- Folic acid
- Prophylactic penicillin until age 5
- Immunizations (pneumococcal, HIB nad meningovax essential)
- Health maintenance – nutrition, social supports, education
- Chronic PRBC (Aim is Hbsickle <30%) – growth failure, frequent hospital admissions, stroke (secondary prevention) or primary prevention (elevated Transcranial doppler or TCD, a measure of risk of hypoxaemic stroke)
- Hydroxyurea: increase HbF and decr frequency of crises = organ protective
- Red cell exchange - quickly reduces HbS
Bone marrow transplant is curative (indicated for ACS, stroke, abnormal TCD)
Sickle cell genetics
b. Single base-pair change
c. Thymine for adenine (GAG to GTG) at the sixth codon of the β-globin gene
- > valine instead of glutamine
Mechanism of action Hydroxyurea + what condition does it treat and what effects does it have?
Used as prophylaxis for sickle cell anaemia
-> Reduces the frequency of painful episodes, Acute chest syndrome, dactylitis
Actions:
- Increases gamma globin, incr prop of HbF (doesn’t include the beta globin) and thus reduces HbS (as in SS you can only make HbS and HbF) so reduces sickling of RBCs
- Improves NO metabolism
- Reduces interaction between RBC and endothelium
Haemophilia A vs B
What is it
How is it inherited
Sx
Ix
Tx
A - Factor 8 deficiency
B - Factor 9 deficiency
-> inability to form fibrin clot adequately
X-linked recessive (male predominant, A - 1/5000 and B -1/30000)
Sx - Delayed bleeding 'Deep' bleeds (joints, muscle - iliopsoas) Spontaneous haemarthoses (ankles, knees, elbows) As neonate may present with intracranial hemorrhage or bleeding w circumscision.
Ix
- decr factor 8 or 9 activity,
- incr/prolongued aPTT -> normalisation with mixing studies
- normal INR/PT
Tx -
Avoid trauma, aspirin/NSAIDs
A: Desmopressin=DDAVP (mild sx) or factor 8 concentrate and tranexamic acid as prophylaxis for more severe form
-> give factor 9 concentrate if Factor VIII Ab present
B: Factor 9 concentrate and tranexamic acid
Presentation of iliopsoas muscle haemorrhage
What condition may be underlying this?
Can result in large amount of blood loss resulting in shock
- Present with vague referred pain in groin, hip held in flexed internally rotated position
- Diagnosis clinically and confirmed with imaging
Haemophilia A or B
Chronic complications of haemophilia
Chronic arthropathy (from inflammation following haemarthosis)
Development of inhibitor to factor 8 (occurrs shortly after factor replacement tx initiated, usually igG ) - usually disappears with continued regular infusions (=immune tolerance)
-> give factor 9 concentrate if Factor VIII Ab present
Transfusion-transmitted infx
Complications of CVC access
Obesity (joint disease)
ITP
What does it stand for?
Pathophys?
Primary vs secondary
Acute vs chronic
Sx
Ix
Tx
Immune thrombocytopaenia (purpura) Problem in primary haemostasis (plt aggregation) IgG against plt aggregation receptor (GP2b/3a) -\> plt destruction
Primary - idiopathic
Secondary to known cause
- Vaccination
- Infection: EBV, chicken pox, HIV, measles
Acute- children (following viral illness)
Chronic - adolescents/adults (50% adol/adults develop chronic following acute episode)
Sx -
- mucocutaneous (superficial) bleeding (petechiae, non palpable purpura, echhymoses)
- 1-4 weeks following viral illness or vaccination
- NO deep bleeding/hemarthosis or systemic signs
Ix
Plt number low (Hb and WCC normal)
Bleeding time prolonged
Normal PT and aPTT
Tx
- *Note - do NOT give plt as will be destroyed*
- Steroids (1mg/kg for 5 days)
- IVIG
- Rituximab for chronic ITP
- Splenectomy only if severe chronic ITP
What is the most common cause of acute thrombocytopaenia in an otherwise well child
ITP
Usually seocndary to viral illness (EBV)
Types of hemolytic disease of newborn
What is another name for HDN?
General pathophys
ABO hemolytic disease
Rh hemolytic disease (more dangerous than ABO!)
HDN = erythroblastosis fetalis
Destruction of fetal RBC by maternal IgG antibodies due to the presence of Ag not present in maternal blood
Ab produced when fetal RBC produce Ag not expressed by the mother
Rh hemolytic disease
Pathophys
What blood groups does it occur in (mo and baby)
Presentation
In-utero maternal blood exchange with the fetus (fetal and maternal blood mixing)
Occurs only in Rh neg mother and Rh pos fetus
First pregnancy - nothing happens to baby.
- Rh neg mo gets exposed to Rh + fetal blood during pregnany at which point she develops Anti-D IgG (or can occur with a transfusion)
- In subsequent pregnancies, maternal Anti-D IgG can cross placenta to attack baby Rh+ -> haemolysis
Presents as jaundice within first 24 hrs of life
Hemolytic anaemia
Hydrops fetalis possible in severe cases
ABO hemolytic disease
Pathophys
What blood groups does it occur in
Presentation
Caused by in-utero maternal blood exchange w fetus
Type O mother (will have anti-A and anti-B Abs), A/B/AB fetus
Mother’s Anti-A and Anti-B IgG crosses placenta -> haemolysis in fetus
Presents as mild juandice within first 24 hrs of life w hemolytic anaemia but NO hydrops fetalis
Prevention of hemolytic disease of newborn (screening)
Tx of hemolytic disease of newborn
Prevention/prenatal
i. Maternal blood group and antibody screening, serial antibody titres if positive or at risk – indirect Coomb’s test
ii. Anti-D 2 x throughout pregnancy
iii. If high antibody titers, measure serial fetal MCA velocities – increased MCA velocity correlates with fetal anaemia
Tx /postnatal
- Delivery at tertiary centre
- Immediate FBE, DCT, BG, SBR on cord sample
- Serial SBR
- Phototherapy
- Exchange transfusion if severe (rids of maternal Ig)
- PRBC transfusion in severe anaemia (match to mothers blood)
DIC pathophys
Widespread thrombohaemmhoragic disease resulting from any life-threatening systemic disease assoc w hypoxia/acidosis/tissue necrosis, leading to endothelial damage
- > widespread activation of clotting cascade
- > Widespread microvascular thrombosis -> haemolysis due to mechanical obstruction of RBCs by thrombosis in small vessels
- > excessive consumption of clotting factors leads to deficiency of plt and clotting factors (↓ plt, ↓ fibrinogen, prolongued INR/PT/APTT, ↓ fibrin degradation product)
- > haemmhorage/bleeding
- > shock
Triggers of DIC
any life-threatening systemic disease assoc w hypoxia/acidosis/tissue necrosis, leading to endothelial damage and activation of coag cascade
Pregnancy
Malignancy (esp haematological)
Sepsis
Trauma
Shock/asphyxia
Snake/insect bites
Certain haem disorders
Presentation of DIC
a. Accompanies a severe systemic disease process, usually with shock
b. Bleeding frequently first occurs from sites of venepuncture or surgical incision
c. Petechiae, ecchymoses
d. Tissue necrosis – infarction of large areas of skin, subcutaneous tissue, kidneys
e. Anaemia secondary to haemolysis may develop rapidly owing to microangiopathic anaemia
Treatment of DIC
- Treat trigger (ex infx)
- Treat shock/acidosis/hypoxia
- Blood component replacement tx
- FFP for APTT and INR (contains coagulation factors)
- cryoprecipitate for fibrinogen (aim >1.0)
- platelets for thrombocytopaenia (aim > 50)
- consider FIIa
- consider heparin if not bleeding (in chronic DIC)
Ix for DIC
FBE - low HB, plt
Film - schistocytes (fragmented, burr and helmet shaped RBC)
Coag factors 2, 5, 8 reduced
APTT and PT/INR prolongued
High d-dimer
What conditions give the following:
Prolonged aPTT
Normal PT/INR
a) aPTT corrects with mixing study
b) aPTT does not correct with mixing study
Intrinsic and common pathway problem
a) corrects -> Factor deficiency (haemophilia)
b) does not correct -> inhibitor present, such as heparin or Antiphospholipid antibody syndrome (lupus anticoagulant)
What conditions give the following:
Normal aPTT
Prolonged PT/INR
Note PT/INR reflect the extrinsic pathway, involves factor 7 and tissue factor release following endothelial/tissue damage
Factor 7 deficiency
Liver disease
Warfarin effect
Vitamin K deficiency
What conditions give the following:
Prolongued aPTT
Prolonged PT/INR
Multiple factor deficiencies
Liver disease
Warfarin
Vitamin K deficiency
DIC (consumption)
Inhibitor to multiple steps in coagulation cascade (heparin, APL ab syndrome)
What sort of anaemia does lead poisoning give you and why?
What is the typical presentation
What ix would you perform
What is the management?
Microcytic sideroblastic anaemia due to defective heme molecule synthesis
Lead blocks an enzyme involved in the production of the heme molecule
Presentation:
In setting of old houses with chipping paint
Dark pigmentation in gingiva of gums (Burton lines)
Can also see lead on metaphysis on long bones on Xr
CNS changes
Abdo pain
Ix
- Plasma lead levels
- Blood smear - microcytic aneamia with sideroblasts (ringed appearance of nucleus of RBC)
Mx
- Lead chelation
(Succimer in kids -> ‘sucks the lead out’)
What is sideroblastic anaemia
Mechanism
Causes
Ix
Bone marrow produces RINGED SIDEROBLASTS instead of normal RBCs
Type of microcytic anaemia caused by disordered haem synthesis
Mechanism - defect in an enzyme involved in production of heme molecule and incorperation of Fe
Underlying causes
- Genetic (x-linked)
- Acquired (Myelodysplasia, malignant disease of BM)
- Reversible
- Alchohol
- LEAD POISIONING
- Vitamin B6 deficiency
- Cu deficiency
- Medications (isoniazid)
Ix
- Microcytic hypochromic anaemia
- ELEVATED ferritin and iron (as unable to incorporate the iron into Hb)
- Peripheral smear: basophilic stippling if lead poisoning
- Bone marrow smear: ringed sideroblasts
Clinical features of TAR syndrome and classic age of presentation
Severe thrombocytopaenia at birth or in the first week (tends to freq remit over first few years of life)
Bilateral absent radii - Thumbs ALWAYS present
- 50% have leg involvement: patella, hip, knee dislocations, tibial torsion
Congenital heart disease in 1/3 of patients
CMPI (present in 50-100%)
B12 deficiency
- Changes on blood film
- What inv confirms diagnosis?
- What is mx of B12 clinical deficiency
Hypersegmented neutrophils
Oval macrocytes
Macrocytic anaemia - large, darkly coloured RBCs
Low Active B12 or Elevated serum methylmalonic acid level confirms diagnosis (NOT total B12)
Mx
- Infants + older pts with neurological sx: replacement with IM B12
- Older children/low risk: oral replacement
Folate def
Ft on blood film and FBE
FBE = macrocytic anaemia, low reticulocytes +/- neutropaenia +/- thrombocytopaenia
i. Note: acute folate deficiency not macrocytic
Film = nucleated RBC with megaloblastic morphology, variation in RBC size/shape, neutrophils large some with hypersegmented nuclei
Serum folic acids levels = < 3ng/ml (normal 5-20ng/ml)
RBC folate= is a better indicator of chronic deficiency (normal 150-600ng/ml)
Asplenia
- causes
- complications/risks assoc w asplenia
- Blood film feature
Congenital absence
Splenectomy
Infarct of spleen (sickle cell can cause this)
Infiltration (amyloid, sarcoid)
Functional
- prematurity
- malaria
- post-radiation
- overwhelming of reticuloendothelial function (Severe hemolytic anaemia)
Decr splenic function leads to incr risk of infection (polysarrcharide encapsulated eg: Streptococcus pneumoniae, Haemophilus influenzae, and N. meningococcus)
AND incr risk of thromboembolic disease (loss of filtration of abnormal RBCs -> clots)
Blood film feature : howell-jolly bodies
Presentation G6PD
Diagnostic ix of choice?
Findings on blood film
X-linked recessive condition of G6PD enzyme deficiency
Presentation
- Neonatal jaundice (rarely w anaemia), days 2-3 of life
- Episodic haemolytic anaemia w classic precipitants that cause oxidative stress (sepsis, drugs like antimalarials, bactrim, moth balls, fava beans)
Ix: macrocytic anaemia w reticulocytosis during crisis, haemoglobinuria (intravascular haemolysis)
Diagnostic is G6PD red cell enzyme levels (low)
Blood film
- Blister/bite cells
- Heinz bodies
Complications/presentations of Sickle cell anaemia
Ft on blood film
Vaso-occlusive cx
-> Lung blood vessels
= Acute chest syndrome (50% of pts w SCA)
-> Bones of hands and feet = dactylitis
-> Other bones (most common)
= bone/joint infx (if septic, think salmonella!)
= pain crisis
= avascular necrosis (hip/head of femur)
-> Spleen
= Infarct
= Splenic sequestration (leads to anaemia, thrombocytoaenia and splenomegaly) -> hypovolaemic shock
= Auto-splenectomy from fibrosis
= Susceptible to encapsulated bacteria (strep pneum, H infl, N men, salmonella)
-> Cerebral vasculature
= stroke (5-10% of pts w SCA) - do NOT give tPA, will cause them to bleed! Silent infarcts can cause poor school performance (high TCD = higher risk of stroke; give transfusion or hydroxyurea to prevent this)
= moya-moya
-> Renal papilae
= necrosis -> hematuria, proteinura, AKI
-> Penis
= priapism (prolongued/painful erection)
Triggers:
- PARVOVIRUS infx
- Infection
- Cold
- Hypoxia
- Dehydration
Pyruvate Kinase deficiency
- what is it?
- sx
- ix
- mx
AR condition resulting in deficiency of pyruvate kinase enzyme resulting in rigid abnormal RBCs which are prematurely destroyed via autohaemolysis
Sx: mild sx of anaemia due to compensatory incr in 2,3DPG which helps with O2 offloading into tissues
- Jaundice
- Splenomegaly
- Gallstones
Ix
- Macrocytic anaemia with reticulocytosis
- FIlm: Echinocyte/Burr/Prickle cell, poikilocytes (abnormal shape), anisocytosis (uneven sizes), reticulocytes
- Diagnosis via RBC enzyme assay of PK levels (low)
Mx (same as hereditary spherocytosis)
- Transfusions as necessary
- Splenectomy if necessary (>6yo)
- Folic acid supplementation
What is this?
Sickle cell anaemia
Blood film features: sickled cells, target cells, howell jolly bodies
What is this condition?
Iron deficiency anaemia
Features
- Microcytic and hypochromic red blood cells
- Secondary thrombocytosis which differentiates it from beta thalalassaemia
- Unlike thalassemia: you usually DON’T have target cells, and anisocytosis (abnormal variation in the size of RBC) and poikilocytosis (abnormally shaped RBC) are not marked
What is this condition?
Hereditary spherocytosis
In microscopical blood smear evaluation, spherocytic red blood cells appear as smaller round cells lacking the normal central pale area due to the absence of a normal biconcave shape.
Presentation: The classic triad in a child is of jaundice, anemia, and splenomegaly. The most common finding in neonates is jaundice.
What is this condition?
Thalasseaemia
Features
Microcytic and hypochromic red blood cells
- Target cells
- Anisocytosis (abnormal variation in the size of RBC)
- Poikilocytosis (abnormally shaped RBC - tear drop cells)
- Erythroblasts (nucleated RBC precursor)
What is this condition?
- bite cells
- blister cells
- heinz bodies
- target cells
- reticulocytes
What is this condition?
Megloblastic anaemia secondary to B12 deficiency
- macrocytic (large oval) RBCs
- hypersegmented neutrophils
this blood film + easy bruising; grey hairs, pale eyes and skin and frequent pyogenic infecitons =?
What are the other features and ix findings characteristic of this condition?
Chédiak-Higashi syndrome (CHS)
Diagnosis is made by recognition of the characteristic giant granules in neutrophils, eosinophils, and granulocytes on blood film
Other laboratory findings include neutropenia and hypergammaglobulinemia
partial oculocutaneous albinism, frequent pyogenic infections, silvery hair, photophobia, nystagmus and hepatosplenomegaly.
HbA
HbA2
HbF
HbE
HbA2 elevated in beta thal
