Anaemia AB Flashcards
What is the main source of iron for haematopoiesis?
Recycled iron from reticuloendothelial system
Where is most of the body’s iron stored?
Hb in circulating red cells
What regulates iron absorption?
1) Oxygen tension
2) Intracellular iron levels
3) Systemic iron needs
What is the role of hypoxia-induced factor?
Hypoxia-induced factor (HIF-2a)
- induced by reduced oxygen tension
- transcriptional control of DMT-1 and ferroportin
What is the role of iron regulatory proteins?
Iron regulatory proteins type 1 and 2 (IRPS1/2)
- responds to intracellular iron level
- binds to iron-response elements that impact on mRNA stability and translation
What is the role of hepcidin?
Hepcidin: binds to ferroportin and induces its degradation
- Systemic regulation of iron absorption; liver production
- Regulated by: HFE, TfR2, HJV, inflammation, hypoxia, EPO
- Acute phase reactant, largely mediated by IL-6
How do hepcidin levels differentiate between iron overload and iron deficiency?
Iron overload: hepcidin increased
Iron deficiency: hepcidin reduced
Where is iron absorbed?
Duodenum
Iron deficiency anaemia - what do you see on blood film?
Microcytic, hypochromic cells, pencil cells, thrombocytosis, increased RDW
Iron deficiency anaemia - what do you see on iron studies?
Transferrin increased Transferrin saturation decreased TIBC increased Ferritin reduced Soluble transferrin receptor increased (less specific than low ferritin)
Anaemia of chronic disease - what is the mechanism?
IL-6»_space; increased hepcidin»_space; ferroportin degraded
Altered or abnormal iron haemostasis
- reduced absorption or trapping in macrophages
Reduced red cell production by bone marrow
- toxicity/cell death of precursors; CK mediated effect
Blunted response to EPO
- reduced production of EPO, reduced receptors, reduced responsiveness
Shortened red cell survival
- erythrophagocytosis; CK and free radical damage
How does soluble transferrin receptor differentiate iron deficiency from anaemia of chronic disease?
Increased in iron deficiency anaemia
Normal in anaemia of chronic disease
What factors affect the level of soluble transferrin factor?
Soluble transferrin receptor is derived from bone marrow erythroid precursors
Directly proportional to erythropoietic rate
Inversely proportional to iron stores
Blood film - what is the cause of ovalocytes?
Megaloblastic anaemia
Megaloblastic anaemia - which drugs cause this?
Antifolate drugs
- MTX, pentamidine, TMP
DNA synthesis
- AZA, hydroxyurea, Zidovudine, chemo
Macrocytic anaemia - what are the causes?
B12/folate deficiency Drugs (antifolate, DNA synthesis) Reticulocytosis BM pathology (MDS, myeloma, aplastic anaemia) Liver disease, EtOH, phenytoin Copper deficiency Arsenic Down syndrome
Macrocytic anaemia - what are some factitious causes?
Cold agglutinins
Old sample
Hyper-osmolar state
B12 - where is it absorbed?
Terminal ileum
B12 - how is it absorbed?
Initially bound by transcobalamin I or haptocorrin (R protein)
Pancreatic enzymes release cobalamin from these and allow binding to intrinsic factor from gastric parietal cells
B12-IF complex binds to receptor (cubulin) in terminal ileum, taken up by receptor-mediated endocytosis and absorped into portal circulation
Pernicious anaemia - what is the mechanism?
Autoimmune destruction of gastric mucosa/parietal cells
Leads to reduced acid production and reduced IF
Pernicious anaemia - what are the associations?
Blue eyes, fair hair, northern european Family history Blood group A Vitiligo, thyroid disease, Addison's, hypoparathyroid Hypogammaglobulinaemia Gastric carcinoma
Pernicious anaemia - what investigations can you do?
Intrinsic factor antibodies - very specific but only 50% sensitive
Parietal cell antibodies - sensitive but not specific (positive in 15% of normal females)
B12 deficiency - causes?
Pernicious anaemia Nutritional (strict vegans) Ileal pathology - Crohn's - Ileal resection - Tropical sprue/tapeworm - Mutation/deficiency of receptor for IF Gastrectomy Other - NO poisoning - Congenital abnormalities
B12 deficiency - what are the features on blood film?
Macrocytic anaemia Hypersegmented neutrophils - May develop before anaemia develops Oval macrocytes Low reticulocyte count Pancytopaenia may occur
Folate - what is the source?
Dietary (only)
Folate - where is it absobed?
Small bowel
Folate - how long do the stores last?
Months
Folate - where is it stored?
> 95% in RBC
Decreased haptoglobin - what are the causes
Haemolysis Liver failure Megaloblastic anaemia Anaemia of chronic disease Congenital
Microangiopathic haemolytic anaemia - what are the causes?
TTP/HUS Atypical HUS Pre-eclampsia HELLP Malignant hypertension Renal allograft rejection
Atypical HUS - what is the cause?
Inherited dysregulation of complement system
Atypical HUS - what is the treatment?
Eculizumab
TTP - what is the classic pentad?
Haemolysis with red cell fragmentation Thrombocytopaenia Fever Neurological signs Renal impairment
TTP - what is the pathogenesis?
- ADAMTS13 deficiency (hereditary or acquired); protease that cleaves vWF
- Increased high molecular weight vWF
- Abnormal platelet aggregation
- Microvascular thrombosis
- Tissue ischaemia
TTP - what are the causes?
Idiopathic Pregnancy Drugs (CsA, chemotherapy) Bone marrow transplant Malignancy HIV Familial
TTP - what is the mortality if untreated?
> 90% - haematologic emergency
TTP - what is the treatment?
PLEX
Avoid platelet transfusions
Immunosuppression
PNH - what is the genetic basis?
Rare, acquired clonal disease of haematopoiesis
Somatic mutation in pig-A gene
PNH - what is the mechanism?
Defective production of phosphatidylinositol glycan A (PIG-A) which is essential for the formation of the GPI anchor
Loss of several surface proteins that protect the cell from complement-mediated lysis: CD55, CD59
PNH - what is the diagnosis?
Flow cytometry (gold standard)
- CD55 and CD59 on RBC + neutrophils
- FLAER
PNH - what is the treatment?
Transfusions; SCT
Thrombosis management - lifelong after 1st thrombosis
Eculizumab: anti-C5 (targets terminal component of C’ cascade)
Paroxysmal cold haemoglobinuria - causes?
Idiopathic
Syphilis
Viral infections
Paroxysmal cold haemoglobinuria - mechanism?
Biphasic IgG anti-P antibody (Donath-Landsteiner Antibody) binds RBC at low temperatures
Upon warming, C’ mediated lysis occurs
Paroxysmal cold haemoglobinuria - blood film?
Red cell agglutination
Paroxysmal cold haemoglobinuria - management?
Cold avoidance
Splenectomy NOT useful
Spherocytes - what conditions are they found in?
AIHA
Hereditary spherocytosis
Warm AIHA - what are the 6 causes?
Idiopathic SLE/autoimmune Lymphoproliferative: CLL/lymphoma Infection: HCV, CMV Drugs: methyldopa, antibiotics Evan's syndrome: combination of autoimmune haemolysis with ITP
Warm AIHA - what is the mechanism?
Antibodies that react with red cells at 37 degrees- IgG*** +/- complement
- RBC taken up by macrophages in the RE system via Fc receptors
Warm AIHA - what are the investigations?
Direct antiglobulin test (Coombs test)
- Demonstration of autoantibodies attached to the patient’s red cells
DAT - what are the causes of false positive and false negatives?
False positives: 10% of hospitalised patients
- Recent transfusion - delayed haemolytic transfusion reaction
False negatives:- IgA or IgM mediated
Warm AIHA - what is the treatment?
Prednisolone 1mg/kg then taper- First line
IVIG
Folate supplement
Immunosuppression: AZA/6MP
Splenectomy and vaccination - Best second line after steroids
Rituximab
Warm AIHA - what are the characteristic findings?
Anaemia
Haemolysis
Spherocytes
Splenomegaly
Cold AIHA - what is the mechanism?
Antibodies that react with RBCs
Cold agglutinin disease - what are the causes?
Primary
- Associated with MGUS or asymptomatic LPD
Secondary (majority)
- LPD
- Mycoplasma
- EBV
- Autoimmune
Cold agglutinin disease - treatment?
Cold avoidance
Chlorambucil if underlying LPD
Rituximab
Does NOT respond to steroids or splenectomy
Hereditary spherocytosis - what is the pathology?
Loss of VERTICAL interactions
Ankyrin 50%
Spectrin 30%
Band 3 20%
Hereditary elliptocytosis - what is the pathology?
Loss of HORIZONTAL interactions
Alpha or beta spectrin
Protein 4.1
Band 3
South-East Asian Ovalocytosis - what is the pathology?
Band 3 abnormality
Hereditary spherocytosis - what is the genetic inheritance pattern?
Autosomal dominant - Family history in 75%
Hereditary spherocytosis - what is the typical presentation?
Haemolysis of varying intensity, exacerbated by intercurrent illness
Jaundice
Cholelithiasis
Splenomegaly
Hereditary spherocytosis - what is on the blood film?
Polychromasia
Prominent spherocytes
Note - typical film and FHx sufficient to establish diagnosis
Hereditary spherocytosis - DAT positive or negative?
Negative
Hereditary spherocytosis - flow cytometry findings?
Eosin-5-maleimide (EMA) binding
- Reacts covalently with band 3 protein
Hereditary spherocytosis - management?
Folate supplementation
Splenectomy
Bite cells - what condition are they found in?
G6PD deficiency
The ‘bites’ result from removal of denatured Hb by macrophages in the spleen
Prickle cells - what condition are they found in?
Pyruvate Kinase deficiency
G6PD - what is the pathway involved?
Hexose-monophosphate pathway: pentose phosphate pathway
G6PD deficiency - how does the haemolysis present?
Acute haemolytic crisis
Blood film: bite cells, blister cells
G6PD deficiency - what is the genetic inheritance and prevalence?
X linked
Common
G6PD deficiency - what is the mechanism of RBC damage?
Susceptibility to oxidative stress
Pyruvate kinase deficiency - what is the pathway involved?
Glycolytic pathway
Pyruvate kinase deficiency - how does the haemolysis present?
Chronic haemolysis
Pyruvate kinase deficiency - what is the mechanism of RBC damage?
Reduced ATP formation»_space; RBC rigidity
Pyruvate kinase deficiency - what is the genetic inheritance and prevalence?
Autosomal recessive
Rare
G6PD deficiency - how to you test for this and what may cause false negative results?
Enzyme assays
False negative if reticulocytosis (have higher G6PD levels)
G6PD deficiency - what are the precipitants?
Acute illness/infection Antimalaria drugs - primaquine Sulphur containing drugs - bactrim, dapsone Aspirin Vitamin K analogues Fava beans Probenecid
Immune thrombocytopaenia - what are the associations?
AIHA CLL Autoimmune disease (RA, SLE) H pylori Hep C
Immune thrombocytopaenia - what is the management?
Observation if Plt >30
First line: Prednisolone 1-2mg/kg
IVIG
Splenectomy with vaccination (most effective)
New drugs:
Romiplostim: TPO receptor antagonist
Eltrombopag: TPO mimetic
Other options:
Immunosuppressive: AZA etc
Rituximab
Danazole
DIC - what is the prognostic significance in sepsis and severe trauma?
Independent predictor of mortality
DIC - what are the causes?
Sepsis Trauma Malignancy Pancreatitis Obstetric (amniotic fluid embolus, abruption, HELLP) Liver failure Snake venom
DIC - what is the management?
Platelet transfusion
FFP (coagulation factors)
Cryoprecipitate (fibrinogen)
HIT - what is the mechanism?
- IgG Ab recognises heparin-PF4 complexes
- PF4-Heparin-IgG complex bind to platelet surface
- Platelet activation and consumption via Fc receptor
HIT - at what time in heparin therapy does it typically develop?
5-14 days after commencing heparin
HIT - what are the features?
Plt fall by >50% but severe thrombocytopaenia uncommon
HIT - what is the management?
Cease Heparin
Anticoagulate with direct thrombin inhibitor (Bivalirudin, Argatroban)
HIT - how do you diagnose?
HIT pre-test probability score (4T score)
- Thrombocytopaenia, Timing, Thrombosis, oTher causes
Immunoassay to detect HIT Ab that binds to PF4
- High Sn, low Sp
Functional assay:
- Serotonin release assay (SRA)
- Heparin-induced platelet aggregation (HIPA)
Target cells - causes?
Hb disorders - Thalassaemia
Iron deficiency
Liver disease
What chromosome is Hb alpha on?
Chromosome 16
What chromosome is Hb beta on?
Chromosome 11
Alpha 0 thal - what is the genetic abnormality?
Deletion or inactivation of both alleles on a single chromosome
Alpha + thal - what is the genetic abnormality?
One allele inactivated on the same chromosome
Beta 0 thal - what is the genetic abnormality?
Abnormal gene is not expressed
Beta + thal - what is the genetic abnormality?
Reduced expression of abnormal gene
What is in Hb barts?
4 gamma chains
What is in HbF?
2 alpha, 2 gamma chains
What is in HbA?
2 alpha, 2 beta chains
What is in HbH?
4 beta chains- In alpha thalassaemia (a - / - - )
What is the clinical significance of HbH?
High oxygen affinity
Inclusion bodies
Unstable tetrameres
Haemolysis
What is in HbA2?
2 alpha, 2 delta chains- Increased in beta thalassaemia
What are findings on HPLC in beta thalassaemia trait/minor?
Increased HbA2
Increrased HbF
Iron deficiency can reduce HbA2 so must assess iron status
Beta thalassaemia major - what is the management?
Transfusion support: aiming Hb 9-10 to suppress extramedullary haematopoiesisIron chelation therapy
- Desferrioxamine = survival benefit
- Ferritin >2500 associated with a higher cardiac risk
- Aim ferritin
Desferrioxamine - what are the ADR?
Local reactions (subcut injection) Deafness Retinal toxicity Growth retardation Infections
Sickle Hb - what is the abnormality?
CAG to GTG; B-globin gene
Substitutes valine for glutamic acid (HbS)
HbS polymerizes into long fibres on deoxygenation
RBC: distorted, rigid, damaged membranes
Sickle cell disease - what is the Hb configutaion?
Hb S/S
Hb C/S
Hb beta/S
Sickle cell disease - what is the genetics and prevalence?
Autosomal recessive
Among most common AR disorders
Hyposplenism - what are the features on blood film?
Howell-Jolly bodies
Target cells
Occasional acanthocytes
Lymphocytosis