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haemolytic anaemia Flashcards

1
Q

look in notes for image of normal blood film

A
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2
Q

define haemolytic anaemia

A

anaemia due to a shortened survival of circulating red blood cells due to their premature destruction
this is associated with increased bone marrow activity (erythroid hyperplasia) to compensate for red cell destruction

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3
Q

what is the difference between extravascular and intravascular haemolysis?

A

extravascular

  • destruction of the RBCs by macrophages in the spleen, liver and bone marrow
  • little or no Hb escapes into the circulation as destruction is extravascular so plasma Hb is normal

intravascular

  • red cells lyse in the circulation and release their products into circulation
  • causes complement activation
  • increased plasma Hb
  • excess Hb excreted by the kidneys in the urine
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4
Q

what are the features of haemolytic anaemia?

A

increase RBC destruction causes

  • High LDH (measurement of cell turnover)
  • low haptoglobin
  • high bilirubin - breakdown product of RBC
  • positive DAT (not always)
  • high MCV
  • blood film - spherocytes, polychromasia, RBC fragments

increased RBC production causes

  • high reticulocyte count
  • erythroid hyperplasia in bone marrow which can be seen on bone marrow biopsy which will show high number of precursor cells
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5
Q

what is the direct antiglobulin test (DAT)

A

you take the patients blood and separate the plasma from teh RBCs. if there re anti-RBC antibodies then these will be attatched to the RBCs as well as in the plasma. Add anti-human globulin to the RBCs which will cause agglutination if there are anti-RBC antibodies present. this is a positive test.

see notes for image which explains

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6
Q

what is the indirect antiglobulin test?

A

take the patients blood and separate the plasma from the RBCs
add test red blood cells and antihuman globulin to the plasma (which would contain anti-RBC antibodies if they were present)
if anti-RBC antibodies are present there will be agglutination

look in notes for picture that explains

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7
Q

how are haemolytic anaemias classified?

A

hereditory vs accquired

hereditory

  • abnormalities of RBC interior - enzynpe defects, haemoglobinopathies
  • RBC membrane abnormalities - hereditory sperocytosis, hereditory elliptocytosis

accquired

  • hypersplenism
  • antibody - immune (warm, cold, mixed)
  • mechanical trauma
  • drug induced
  • infections
  • toxins
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8
Q

what are the 2 most common enzyme defects?

A

G6PD deficiency

PK deficiency

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9
Q

outline the epidemiology of G6PD deficiency

A
  • x linked inherited disorder
  • commonest enzyme disorder of red cells
  • high prevelance in middle east, tropical africa and asia
  • ## heterozygosity is associated with resistance to malaria
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10
Q

outline the pathophysiology of G6PD deficiency

A

G6PD is a metabolic enzyme involved in the pentose phosphate pathway which is important in RBC metabolism as it protects the RBC from harmful effects of reactive oxygen radicals and is the only source of NADPH in red cells. It does this through the reduction of free radicals to water which prevents the RBC from harmful effects of the free radical

useful diagram in notes

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11
Q

what are the clinical manifestations of G6PD deficiency?

A

haemolysis which is usually precipitated by oxidative stress - drugs, infections, foods eg. fava beans

neonatal jaundice
anaemia with jaundice in older age

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12
Q

how is G6PD deficiency diagnosed?

A
  • evidence of haemolysis - high LDH, high reticulocyte count, low haptoglobin
  • negative DAT - non immune
  • blood film - blister cells, bite size cells, heinz bodies, non sperocytic haemolytic anaemia (see picture in notes)
  • enzyme assay will give falsely raised levels of G6PD - do not do in an acute crisis
  • genetic testing
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13
Q

how is G6PD deficiency treated?

A
  • prevention of precipitating factors
  • blood transfusion
  • folic acid
  • splenectomy
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14
Q

outline pyruvate kinase deficiency

A

rare autosomal recessive disorder
no PK which causes reduced ATP production in RBCs causing rigidity
clinical manifestations - anaemia, gallstones, jaundice
diagnosis - enzyme assay
treatmnet - folic acid if deficient, may need splenectomy

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15
Q

what is a haemoglobinopathy and what are the most common?

A

abnormalities in Hb chains

sickle cell disease, thalassaemia

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16
Q

what is sickle cell disease?

A

a structural abnormality in the Hb molecule due to an inherited mutation of the globin genes causing a qualitative abnormality of globin synthesis. (the chain is abnormal but there is enough)
it is autosomal recessive
glutamic acid is replaced by valine at position 6 (point mutation) on the beta Hb chain
exposure to low oxygen causes the Hb to precipitate to long crystals causing sickled cells

17
Q

what are the clinical manifestations of sickle cell disease?

A

it is variable depending on the phenotype and genotype

  • signs of haemolytic anaemia
  • signs of vaso-occlusive disease in crisis - painful bony crisis in infants, acute chest crisis (SOB, pain, low sats), stroke, haemolytic crisis…
  • chronic renal impairment
  • infections
  • retinopathy
  • AVN of the joints
  • cardiac disease
18
Q

how is sickle cell disease diagnosed and managed

A

diagnosis

  • HPLC - high performance liquid chromatography
  • Hb gel electrophoresis

management

  • folic acid
  • prophylactic antibiotics
  • transfusion
  • ACE inhibitors in nephopathy
  • hydroxycarbamide
  • bone marrow transplant in children and adolescents
  • there are also now some new drugs on the market
19
Q

what is thalassaemia?

A

inherited mutation of globin genes leading to a quanative abnormality of Hb chains (not enough)

20
Q

what are the different types of thalassaemia?

A
  1. reduced synthesis of a normal globin chain
    - alpha + thalassaemia
    - beta + thalassaemia
  2. absent sysnthesis of a normal globin chain
    - alpha 0 thalassamia
    - beta 0 thalassaemia
  3. unequal alpha and beta Hb chain production
21
Q

what are the symptoms of beta thalassaemia?

A

beta thalassaemia is split into 3 types depending on the severity of symptoms:

beta thalasaemia major

  • presents early in life
  • failure to thrive
  • poor weight gain
  • developmental delay
  • hameolytic anaemia
  • jaundice
  • extramedullary haematopoiesis
  • need regular blood transfusions and other treatmnet as this is life threatening

beta thalassaemia intermedia

  • variable presentation
  • severe or mild anaemia
  • some may need regular blood transfucions and other medical treatment

beta thalassaemia minor

  • mild asymptomatic anaemia
  • treatment is not useually required

beta thalassaemia carriers are normally healthy and unaware that they are a carrier unless they have a specific blood test. Their red cells may be slightly smaller than normally meaning sometimes they are falsely diagnosed with iron deficiency anaemia.

22
Q

what are the different types of alpha thalassaemia?

A

there are 2 genes associated with alpha thalassaemia (HBA1 and HBA2) of which you have 2 alleles of each (4 alleles total). Depending how many alleles are faulty will determine the type and severity of alpha thalassaemia:

  1. alpha thalassaemia silent carrier - 1 allelle is faulty and this normally does not cause any signs or symptoms
  2. alpha thalassaemia carrier - 2 alleles are faulty and this causes few or no health problems. possible mild anaemia
  3. haemoglobin H disease - 3 alleles are faulty. this causes moderate to severe anaemia
  4. alpha thalassaemia major - all 4 alleles are faulty. This is also called Hb barts and is incompatible with life
23
Q

how is thalassaemia treated?

A
  • regular blood transfusions (3-4 weekly) to present extramedullary haematopoiesis however this has a risk of iron overload
  • iron chelation therapy - due to regular blood transfusions
  • folic acid
  • prophylactic antibiotics
  • gene therapy
  • allogenic stem cell transplant
24
Q

what are the 2 most common membrane defects of RBCs?

A

hereditory spherocytosis
hereditory elliptocytosis

look in notes for useful diagram of RBC membrane

25
Q

outline hereditary spherocytosis

A
  • autosomal dominant condition
  • Deficiency of beta spectrin or ankyrin makes the RBC more spherical instead of a biconcave disk which causes deformability of RBCs whilst passing through microcirculation. Spherocytes are phagocytosed by macrophages and destructed in spleen hence reduced life span
  • clinical presentation - presents as severe anaemia and jaundice in neonatal period and a variable presentation in childhood (mild - asymptomatic, moderate - intermittent jaundice, splenomegaly, anaemia, severe- jaundice, gallstones, bone expansion, transfusion dependant)
26
Q

outline hereditary elliptocytosis

A
  • autosomal dominant
  • functional abnormality in one or more anchor proteins in RBC membrane causing elliptical RBCs
  • clinical manifestations - vary from asymptomatic to sever haemolysis depending on genotype
  • treatment - folic acid, blood transfusion, splenectomy
27
Q

what are the 2 types of autoimmune haemolytic anaemia?

A

warm antibodies
cold antibodies
(may also sometimes have a mixed picture)

28
Q

what are warm antibodies?

A

anti-RBC antibodies which are normally IgG. They bind to RBCs at 37C body temp causing jaundice and acute onset haemolytic anaemia.

29
Q

how is warm antibody haemolysis diagnosed?

A

blood film - spherocytes and macrocytes (in notes)

DAT - may be positive or negative depending on cause

30
Q

what are the causes of warm antibody haemolysis?

A

primary

seccondary

  • drugs - penicillin, interferon
  • malignancy - CLL, Lymphoma
  • infection - Hep C, HIV, CMV
  • immune - SLE, ulcerative collitis
31
Q

how is warm antibody haemolysis treated?

A
  • treat underlying cause
  • rituximab
  • prednisolone short term
  • immunosuppresive medications
  • splenectomy
  • transfusion for life threatening complications but all units will be incompatible so needs to be specially treated
32
Q

what is cold antibody haemolysis?

A

IgM antibodies bind to RBCs at 4C as IgM has a lower affinity and only binds at cooler temperatures.

presents as haemolytic anaemia and acrocyanosis (cold and painful blue fingers, ears, toes and nose)

33
Q

how is cold antibody haemolysis diagnosed?

A

DAT - positive for C3D

blood film - red cell agglutination,

34
Q

what are the causes of cold antibody haemolysis?

A

primary

seccondary

  • malignancy
  • infection
  • autoimmune disorder

PCH

35
Q

how is cold antibody haemolysis treated?

A
  • keep patient warm
  • transfuse through blood warmer
  • folic acid
  • treat underlying disease
  • rituximab
36
Q

what are the alloimmune causes of haemolytic anaemia?

A
  • haemolytic disease of the newborn - Rh negative mother has Rh positive baby
  • haemolytic transfusion reaction
  • post allogenic HSCT
37
Q

what is microangiopathic haemolytic anaemia?

A

intravascular haemolysis caused by mechanical injury if the RBC whilst passing through fibrin strands deposited in the vessel

blood film - shows RBC fragments and low platelets

causes

  • Haemolytic uraemic syndrome
  • Thrombotic thrombocytopenic purpura
  • Pre-eclampsia
  • Disseminated carcinoma
  • Collagen vascular disease
  • Medications
  • Malignant hypertension

This is an emergency

38
Q

what is thrombotic thrombocytopenic purpura?

A

deficiency of ADAMTS13 which cleaved VWF causing platelet aggregation and consumption
it is a haematological emergency which presents with a pentad of
- MAHA
- thrombocytopenia
- fever
- renal failure
- neurological symptoms

haematology (5 decks)

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