JC48 (Medicine) - Hemolytic anaemia, Aplastic anaemia, Inherited anaemia Flashcards
Inherited causes of haemolytic anaemia
RBC Membrane defect:
- Hereditary spherocytosis
- Hereditary elliptocytosis
RBC enzyme deficiency
- G6PD deficiency
- Pyruvate kinase/ glycolytic enzyme deficiency
- Pyrimidine 5’ nucleotidase deficiency
Haemoglobin defect
- Thalassaemia
- Abnormalities: e.g. Sickle cell disease
acquired causes of haemolytic anaemia
Immune
- Autoimmune - Warm or Cold
- Alloimmune: Transfusion reaction or Hemolytic disease of Newborn
- Drug induced hemolysis
Non-immune:
- Mechanical: Prosthetic valves, microangiopathic (DIC, TTP)
- Infection: bacteria (C. perfringens) and parasites (malaria)
- Chemical: Wilson’s disease, Heat, venom, Oxidative drugs, chemicals >>> damage Hb, cell membrane
Acquired intrinsic red cell defect:
- Paroxysmal nocturnal hemoglobinuria
Paroxysmal nocturnal hemoglobinuria
Pathogenesis
PIGA gene mutation > deficiency of glycophosphatidylinositol > Deficiency of CD55, CD59 > RBC membrane defect > complement mediated lysis of RBC
Features of haemolytic anaemia on Lab tests: CBC, Serum, PBS
Evidence of RBC destruction:
- High LDH
- High unconjugated bilirubin
- Low haptoglobin
- High methaemalbumin
RBC changes:
- Fragmentation (microangiopathic hemolysis)
- Agglutination (cold agglutinin disease)
- Spherocytes (hereditary or immune-mediated)
- Positive DAT
Bone marrow compensation:
- Reticulocytosis/ Polychromasia on PBS
- Bone marrow erythroid hyperplasia
History taking for hemolytic anaemia
- Age, Sex, Ethnicity
- Infections (HIV, C. perfringens, Mycoplasma), Travel History (Malaria)
- Drug use (L-dopa, methyldopa, mefenamic acid, penicillin, quinidine)
- Haematological malignancies, autoimmune diseases
- Transfusion history
- Metabolic disease/ Wilson disease/ IEMs (enzyme defects)
- Surgical history: prosthetic valves/ filters
- Gallstone history (portal hypertension, hypersplenism)
General clinical features of hemolytic anaemia
Pallor
Jaundice (no obstructive jaundice signs as unconjugated bilirubin only)
Haemoglobinuria (intravascular hemolysis/ G6PD…etc)
Splenomegaly
Immune haemolytic anaemia
- Cause
- Categorize causative antibodies
- Pathogenesis of drug-induced haemolysis
Autoimmune antibodies against self RBC
Autoimmune:
- Warm IgG
- Cold IgM
Alloimmune: previous sensitization to foreign antigen
- Hemolytic disease of newborn: Rh- or ABO-incompatibility between mother/ child
- Hemolytic transfusion reaction: ABO-incompatibility
Drug induced:
- Alteration of RBC antigen causing AutoAb cross-reaction with normal antigens
- Hapten reaction: associate RBC structures forming part of antigen
Compare underlying causes of Warm and Cold type autoimmune haemolytic anaemia
Warm antibodies (80%): binds best at 37oC, majority IgG, often against Rhesus antigens
- Idiopathic (50%)
- Preceding viral infection: usually in children
- Autoimmune disease, eg. SLE, ALPS
- Immunodeficiencies, eg. CVID
- Lymphoproliferative disease, eg. CLL, NHL
Cold antibodies (20%): binds best at 4oC, usually IgM and binds complement
- Idiopathic
- Infections, esp M. pneumoniae, EBV
- Lymphoid malignancies, eg. monoclonal gammopathies, NHL, CLL
Investigations for diagnosis of AIHA
CBC - Anaemia, usually normocytic
PBS - Reticulocytosis + spherocytosis
Serum - High unconjugated bilirubin, High LDH, Low hepatoglobin
Direct antiglobulin test/ Coombs’ test: positive
Compare direct and indirect antiglobulin tests (/)
Direct Coombs test: useful in detecting prior Ab binding to RBC using anti-IgG, anti-C3
- Autoimmune hemolytic anaemia
- Hemolytic disease of newborn
- Transfusion reactions
Indirect Coombs test: useful in detecting autoreactive Ab in serum
- Antibody screening in pre-transfusion tests
- Screening for HDN during pregnancy
Clinical presentation of warm AIHA (/)
Typical S/S of extravascular haemolytic anaemia
Presents as part of:
- Evans syndrome: co-occurrence of ≥2 immune cytopaenias, most often AIHA + ITP
- Lymphoproliferative disease: most commonly in CLL, present with systemic symptoms (eg. LOW/LOA, fever, LN)
Clinical presentation of cold AIHA (/)
Asymptomatic when not exposed to cold
Cold-induced symptoms:
→ Acrocyanosis
→ Livedo reticularis
→ Raynaud phenomenon
→ Cutaneous ulcer/necrosis
→ Pain/discomfort on swallowing cold food/liquids
Haemolytic anaemia: generally extravascular
→ Variable severity from compensated haemolysis to severe haemolytic anaemia requiring transfusion
→ Precipitant: cold ambient temperature, febrile illness
High risk of VTE
Lymphoid malignancy S/S
Mycobacterium pneumoniae infection/ Infectious Mononucleosis S/S
Management of warm AIHA
- Folate supplement
- Decrease further hemolysis/ immunosuppress:
- Oral prednisolone
- Rituximab
- Splenectomy
- Alternative immunosuppressants: azathioprine, cyclophosphamide - Transfusion: test for allo-Ab (T/S)
- Treat underlying causes (e.g. lymphoproliferative diseases)
Management of Cold AIHA
- Folate supplement
- Avoid cold temperature: eg. avoid cold liquid, warm clothing, pre-warmed IV fluid
- Therapy for anaemia:
- Transfusion with prior T/S - Decrease antibody production
- Rituximab/bortezomib-based chemotherapy for idiopathic cases
- Plasmapheresis, IVIg
- Treat underlying lymphoid malignancy
Aplastic anaemia
- Definition
- Causes
Bone marrow hypoplasia/ aplasia causing pancytopenia
- *Primary aplastic anaemia:**
- Primary idiopathic (80%)
- Inherited bone marrow failure syndromes: Fanconi anaemia, Shwachman-Diamond syndrome, Dyskeratosis congenita
- *Secondary aplastic anaemia:**
- Drugs: alcohol, NSAIDs
- Toxins: benzenes, pesticides
- Ionizing radiation
- Infection: sero-negative hepatitis, HIV, EBV
- Acquired clonal abnormalities (PNG, MDS)
List drugs that cause secondary aplastic anaemia (/)
Cytotoxic drugs: anticipated effect with nadir d7-10
Antibiotics, eg. chloramphenicol, sulphonamide
DMARDs, eg. penicillamine, gold
NSAIDs, eg. phenylbutazone, indomethacin, diclofenac
Thionamides, eg. carbimazole, propylthiouracil
Anticonvulsants, eg. carbamazepine, phenytoin
Alcohol
Idiopathic aplastic anaemia
- Pathogenesis
Immune-mediated, T-cell suppression of marrow stem cells
Autoimmunity due to over-expression of HLA-DR2, polymorphisms in perforin gene or TNF-α
Clinical features of Aplastic anaemia
Pancytopenia: recurrent infections, mucocutaneous bleeding, anaemic symptoms
→ Infections: typically bacterial (sepsis, pneumonia, UTI) but invasive fungal infection is deadly
NO lymphadenopathy, NO hepatosplenomegaly → suggestive of haematological malignancies
± Dysmorphic features in the young, eg. thumb abnormality in Fanconi syndrome
± Haemolytic anaemia, thrombosis → suggestive of associated PNH
Aplastic anaemia
First-line investigations and expected results
□ CBC: pancytopenia with normocytic/macrocytic anaemia, reticulocytopenia
□ PBS: NO abnormal cells
□ R/LFT, haemolysis markers, serum B12, RBC folate to r/o alternative causes
□ BM examination: required for diagnosis
→ Profoundly hypocellular marrow with decrease in all elements and replacement by fat/stromal cells
→ Morphologically normal residual haematopoietic cells without megaloblastic haematopoiesis
→ NO BM infiltration by fibrosis/malignancy
□ Other Ix:
→ Autoimmune markers
→ Flow cytometry (↓CD55/59) for PNH
→ Chromosome breakage with diepoxybutane for Fanconi anaemia esp for children
Severity grading for aplastic anaemia
Purpose of grading?
Non-severe:
BM cellularity < 25% + peripheral pancytopenia not as severe as ‘severe grade’
Severe:
BM cellularity <25% + 2 out of 3 of following:
1. Neutrophil < 0.5
2. Platelet < 20
3. Reticulocytes < 20
Very severe:
BM cellularity <25% + 2 out of 3 of following:
1. Neutrophil < 0.2*******
2. Platelet < 20
3. Reticulocytes < 20
Purpose: Severe and very severe need cytotoxic drug treatment
Treatment of aplastic anaemia **
Allogeneic HSCT: 1st line for young adult + matched donor or refractory disease
Immunosuppressive therapy: Tx for >50y or ineligible for HSCT:
- eltrombopag (TPO-agonist) + antithymocyte globulin (ATG) + Cyclosporine A + steroids
Manage cytopaenia:
- Transfusion for packed cells, platelet concentrate +/- iron chelation/phlebotomy
Infection prophylaxis: antifungals, antibiotics
List inherited marrow failure syndromes causing anaemia and pancytopenia
Anaemia only
- Diamond-Blackfan anaemia
- Congenital dyserythropoietic anaemia
Pancytopenia:
- Fanconi anaemia
- Dyskeratosis congenita
- Schwachman-Diamond syndrome
Compare the inheritance patterns between 5 inherited marrow failure syndromes (/)
Compare between pancytopenia vs anaemia only inherited marrow failure syndromes:
- Consequence of BM failure
- Presence of malignancies
- Presence of short telomeres and chromosomal instability
- Number of genes involved
Fanconi anaemia (FA) (/)
- Genetic cause
- Clinical features
- Diagnosis
- Treatment
Cause: mutation in ≥17 FA genes (FANCA-Q, majority AR but FNACB/R XLR)
→ ↓repair of DNA crosslinks
→ ↑genomic instability
→ premature loss of HSCT
→ High risk of CA - MDS (6000×), AML (700×), SCCs
Clinical features: Congenital malformations
- Skin: hyper-/hypopigmentation, café-au-lait spots
- Thumb/radial abnormality: absent/hypoplastic/bifid thumb, absent/hypoplastic radii
- Axial skeleton: microcephaly, triangular facies, short stature
- VACTERL association: vertebral anomalies, anal, congenital heart (usu VSD), trachea-esophageal, renal, limb defects
- BM failure with pancytopenia
Diagnosis: peripheral blood T cells for chromosomal breakage following exposure to diepoxybutane (DEB)
Tx: allogeneic HSCT with androgen Tx
Dyskeratosis Congenita (short telomere syndrome) (/)
- Genetic cause
- Clinical features
- Diagnosis
- Treatment
Cause: mutation in telomere-related genes → premature cell death or genomic instability
Clinical features:
→ Mucocutaneous findings: classical triad of nail dystrophy, lacy reticular hyperpigmentation of upper chest and neck, oral leukoplakia
→ BM failure
→ Lung fibrosis
→ Cancer predisposition: H&N SCC, gastro/oesophageal, anorectal, skin…etc
Dx: clinical + telomeric length analysis + BM hypocellularity
Mx: supportive + allogeneic HSCT if available
Diamond-Blackfan anaemia (/)
- Genetic cause
- Clinical features
- Diagnosis
- Treatment
Cause: genetic mutation affects ribosome synthesis → ↓activation of TP53 tumour suppressor pathway
Clinical features:
Congenital anomalies: mainly in H&N + UL areas
- Craniofacial: hypertelorism, microcephaly, congenital cataract/glaucoma, micro-ophthalmos, blue sclera, high-arched palate, ear malformation
- Thumb: bifid, duplication, hypoplasia, absence, flat hypoplastic thenar eminence
- Urogenital: dysplastic/horseshoe kidney, duplex ureter, RTA
- Others: A/VSD, hypogonadism, mental retardation
Pure red cell aplasia (PRCA) - isolated anaemia
Diagnosis:
isolated macrocytic anemia with onset <1y, no other cytopenias, reticulocytopenia, normal BM cellularity
Tx: transfusion + oral steroid from 6-12mo
History taking for inherited anaemia *
Family history - Pattern of inheritance
Age of onset
Drug Hx
Symptoms of haemolysis
Transfusion requirement
Complications
List 5 inherited RBC membrane defects
Hereditary spherocytosis
Hereditary elliptocytosis and hereditary pyropoikilocytosis
Southeast Asian ovalocytosis
Hereditary acanthocytosis
Hereditary Stomatocytosis
Outline the underlying membrane proteins associated with inherited RBC defects (/)
Hereditary spherocytosis
Definition
Inheritance, genetic defects, pathogenesis
Definition:
hereditary RBC membrane defect characterized by spherocytes on RBCs
AD inheritance
Ankyrin- spectrin complex defect >> abnormal vertical cytoskeleton-membrane interaction >> primary loss of membrane (due to microvesiculation) → progressive spherocytosis
Poor deformability → inability to pass through splenic microcirculation → confers liability to haemolysis
Hereditary spherocytosis
Clinical presentation
Chronic haemolytic anaemia: moderate, with jaundice
Crises of anaemia exacerbation/ Aplastic crisis:
→ Haemolytic crisis due to ↑severity of haemolysis ma/w infections
→ Megaloblastic crisis due to folate deficiency, a/w during pregnancy
→ Aplastic crisis** due to parvovirus B19 infection → severe anaemia with low reticulocyte count
Complications of haemolysis:
- Neonatal jaundice
- splenomegaly
- pigmented gallstones **
Investigations and typical findings of Hereditary Spherocytosis
CBC: anaemia, MCV variable, MCHC ≥36g/dL
Blood film: spherocytes, polychromasia
Bone marrow: erythroid hyperplasia
Markers of extravascular haemolysis:
- ↑LDH, ↑unconj bilirubin
Flow cytometric analysis
- ↓ eosin 5’ melamide (EMA) binding** on red cell skeletal proteins
- *Osmotic fragility test**** (± pre-incubation) when EMA binding N/A:
- ↑fragility compared to normal RBCs when exposed to hypotonic solutions
Treatment of Hereditary spherocytosis
**no specific treatment**
- *Folic acid** supplementation
- *Transfusion** if severe anaemia
- *Splenectomy** for severe haemolysis
- *EPO** for infants
- *Cholecystectomy** if symptomatic gall-stones
(Allogeneic HSCT: NOT used due to unfavourable risk-benefit ratio)
Categorize haemoglobin disorders with examples
List Red Cell Enzymopathies
G6PD deficiency
Pyruvate kinase (PK) deficiency
Deficiencies of other glycolytic pathways
>>> Congenital non-spherocytic haemolytic anaemia
PK deficiency enzymopathy (/)
- Inheritance
- Pathogenesis
- Clinical features
- Dx
- Tx
AR inheritance
Pathogenesis: haemolysis due to PK def, tolerated due to ↑O2 delivery from ↑2,3-BPG
Clinical features: lifelong condition but age of presentation varies
→ Chronic, Coombs’-negative haemolytic anaemia: usually from birth
→ Haemolysis Cx: NNJ, gallstones, jaundice, variable splenomegaly, folate deficiency
→ Iron overload due to ineffective erythropoiesis or transfusional iron overload
Dx: by testing PK activity in RBC haemolysate or genetic testing
Mx: transfusion ± chelation, folate supplementation, splenectomy
G6PD deficiency
- Epidemiology
- Inheritance
- Pathogenesis
- most common RBC enzymopathy, affects 400M worldwide
- Inheritance: X-linked recessive
- Mutation: most commonly G6PD-Canton in China
Haemolysis: occurs during exposure to oxidative stress
→ insufficient regeneration of glutathione due to deficient G6PD activity
→ oxidant accumulation within RBC → oxidization of Hb and other proteins
→ formation of Heinz bodies (clumps of denatured Hb) and bite cells as Heinz bodies are removed by macrophages in RES
→ rigid non-deformable RBC destroyed in RES (extravascular)
5 classes of G6PD (/)
- Class I: G6PD activity <10%, a/w chronic haemolytic anaemia
- Class II: G6PD activity <10%, a/w intermittent haemolysis only with NNJ, Favism, drug-induced intravascular haemolysis
- ****** most common in Chinese with Canton variant ********
- Class III: G6PD activity 10-60%, a/w intermittent haemolysis only
- Class IV (normal): G6PD activity >60%, a/w no clinical significance
- Class V: G6PD activity >100%, a/w no clinical significance
Clinical presentation of G6PD deficiency
Asymptomatic between episodes of haemolysis
- *Acute haemolytic anaemia trigger by infection, critical illness, drugs >> Intravascular hemolysis**
- classically sudden onset of jaundice, pallor, dark urine
- abrupt ↓Hb by 3-4g/dL ± abdominal, back pain (due to haemoglobinuria)
Neonatal jaundice
Triggers of acute hemolysis episodes of G6PD deficiency (/)
Investigations for G6PD deficiency
- Acute hemolytic attacks
- Screening tests in newborn
- Confirmatory tests
Non-spherocytic intravascular haemolysis during attack
→ CBC/PBS: polychromasia with bite cells, hemighosts, ghost cells, Heinz bodies
→ Intravascular haemolysis: ↑LDH, ↑unconj bilirubin, ↓haptoglobin, ↑methaemalbumin, haemoglobinuria/haemosiderinuria ± AKI
Screening test: absence of fluorescence in UV light or failure to reduce methaemoglobin → indicate failure to generate NADPH (semiquantitative)
Confirmatory test: by G6PD assay - test activity directly
Management of G6PD deficiency
□ Avoid haemolysis triggers
□ Transfusion ± aggressive hydration for acute intravascular haemolysis
(Folate supplementation: NOT necessary unless in class I variant a/w chronic haemolysis)
