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Haematology > Haemolysis and Acquired Haemolytic Anaemia > Flashcards

Haemolysis and Acquired Haemolytic Anaemia Flashcards

1
Q

What are the three main functions of the spleen

A
  1. Controls rred cell integrity
  2. Immune Function
  3. Storage Function
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2
Q

Control Red Cell Integrity

A

Pitting

Culling

Grooming

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3
Q

Pitting

A

Removes inclusions such as RNA, siderotic granules etc.

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4
Q

Culling

A

Trap rigid red cells

Remove abnormal / senescent red cells

Hypoxic environment

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5
Q

Grooming

A

Removes excess lipids from reticulocytes

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6
Q

Immune Function

A

Filtration of antigens

Macrophages and dendritic cells

Presentation to T- and B-cells

NB! Encapsulated organisms

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7
Q

Storage

A

Platelets:

About 30% of platelets stored in normal spleen
Can increase to >90% in enlarged spleen

Red blood cells:

236.5 ml (~ one cup) of red blood cells
Released in cases of hypovolemia
E.g. trauma or massive blood loss

White blood cells:

Up to a quarter of lymphocytes
Also neutrophils etc.

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8
Q

Hyposplenism

A

Can be as a result of surgery or could be functional

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9
Q

Hyposplenism:

Causes

A

Splenectomy

Sickle cell disease

Gluten-induced enteropathy

Inflammatory bowel disease

Splenic artery thrombosis

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10
Q

Hyposplenism:

Risks

A

Infections:
-Encapsulated organisms:

Especially Pneumococcus, Haemophillus and
Meningococcus

Vaccinations NB!

Prophylactic antibiotics

Thrombosis:
Consider prophylaxis

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11
Q

Hyposplenism:

Features

A

Raised platelet count or white cell count:
-Usually temporary, but may be persistent

Peripheral smear:
-Acanthocytes, Howell-Jollly bodies, Pappenheimer
bodies, target cells, etc.

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12
Q

Normal Red Cell Destruction

A

Mean lifespan of 120 days

– Red cells have no nucleus
– Metabolism gradually deteriorates
– Cells become non-viable

Cam be removed either Extravascularly/Intravascularly
-Removed extravascularly by the macrophages of the
reticuloendothelial (RE) system, spleen, bone marrow, liver

-Intravascular haemolysis:
Little or no part in normal red cell destruction

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13
Q

Haemolysis:

Heamolytic Anaemia

A

Increased rate of red cell destruction / decreased red cell lifespan

Erythropoietic reserves:

– Potential to expand 6-8 times normal production

Haemolysis if red cell lifespan < 100 days
– Anaemia only occurs when red cell lifespan is less than 30days

Usually compensated initially due to ↑ erythropoietin
– Therefore anaemia may be mild

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14
Q

Haemolytic Anaemia in Adults

A

Anaemia as a result of increased rate of RBC destruction

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15
Q

Causes of Intravascular Haemolysis

A

Mismatched blood transfusions (usually ABO)

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Microangiopathic haemolytic anaemia
– (Red cell fragmentation syndromes)

Autoimmune haemolytic anaemia (Some)

Drugs, toxins and infections (Some)

Paroxysmal nocturnal haemoglobinuria (PNH)

March haemoglobinuria

Unstable haemoglobins

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16
Q

Diagnosis of Haemolytic Anaemia

A

Specific clinical presentation due to increased red cell
destruction and associated increase in erythropoiesis.

Can be acute or chronic

No symptoms are specific for the diagnosis of haemolytic anaemia

Recognition of haemolysis is NOT DIFFICULT in the
classical patient

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17
Q

Clinical Presentation

A

Rapid onset of pallor (anaemia)

Jaundice

History of pigmented
(bilirubin) gallstones

Splenomegaly

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18
Q

Increased Red Cell Destruction:

Clinical/Laboratory Features and Mechanism

A

Pallor of mucous membranes:
↓ Haemoglobin

Jaundice:
↑ Unconjugated serum bilirubin

Dark urine:
(Especially if left to stand) ↑ Urobilinogen

Pigment gallstones:
↑ Bilirubin in bile

Splenomegaly:
↑ Red cell destruction

Absence of plasma haptoglobins:
Removed through hemoglobin/haptoglobin complexes

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19
Q

Increased Red Cell Production:

Clinical/Laboratory Features and Mechanisms

A

Reticulocytosis:
Erythroid precursors in peripheral blood

Folate deficiency:
Increased consumption by high red cell turnover

Bone deformities:
Erythroid hyperplasia of bone marrow lead to expansion

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20
Q

Investigations for Heamolysis

A

Evidence of haemolysis – 3 components

  1. Red cell damage/loss:
    - FBC
    - Peripheral smear
    - Haemosiderinuria
  2. Biochemistry
    - Blood
    - Urine
  3. Increased red cell production
    - Reticulocyte count
    - Peripheral smear
    - Bone marrow
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21
Q

Red Cell Damage/Loss

A

FBC-Full Blood Count

Haemoglobin, haematocrit, other indices:
-Normochromic, normocytic anaemia (May be macrocytic)

Other cell-lines involved:

  • May have reactive leucocytosis/thrombocytosis
  • Evidence of underlying disease process

Peripheral smear:

  • Spherocytes
  • Red cell fragments if microangiopathic

Haemosiderinuria:
-Evidence of intravascular haemolysis

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22
Q

Biochemistry

A

Blood:

  • Raised unconjugated bilirubin
  • Raised lactate dehydrogenase (LDH)
  • Low haptoglobin
  • Low haemopexin

Urine:

  • Haemoglobinuria
  • Urobilinogenuria
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23
Q

Increased Red Cell Production

A

Reticulocyte count:
-Reticulocytosis

Peripheral smear:
-Polychromasia

Bone marrow:
-Erythroid hyperplasia

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24
Q

Immune Heamolytic Anaemia:

Types

A

Autoimmune Haemolytic Anaemia

Alloimmune Haemolytic Anaemia

Drug-Induced Immune Heamolytic Anaemia

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25
Q

Autoimmune Haemolytic Anaemia:

Types

A

Warm Autoimmune Haemolytic Anaemia

Cold Autoimmune Haemolytic Anaemia

26
Q

Warm Autoimmune Haemolytic Anaemia

A

Red cell coated with immunoglobulin and/or complement:
– Usually IgG and C3, rarely IgA

Immunoglobulin recognized by Fc receptor on macrophages in reticuloendothelial (RE) system:
– Loss of membrane leads to spherocytes
– Shortened red cell lifespan

Clinical picture:
– Any age, sex
– Haemolytic anaemia – varying severity
• Remit and relapse
– Splenomegaly
27
Q

Warm Autoimmune Haemolytic Anaemia:

Causes

A
  1. Idiopathic (70% of cases)
2.Secondary
– Autoimmune diseases (SLE etc.)
– Lymphoproliferative disorders:
   *Lymphoma
   *Chronic lymphocytic anaemia
– Viral infections (EBV)
– Drugs: Methyldopa etc.
28
Q

Warm Autoimmune Haemolytic Anaemia:

Clinical Features

A

Pallor

Jaundice:

  • Mild
  • Fluctuating

Dark urine

+- Splenomegaly

29
Q

Warm Autoimmune Haemolytic Anaemia:

Laboratory Findings

A

Full blood count
– Normocytic/macrocytic anaemia
– Leucocytosis

Peripheral smear
– Spherocytes, polychromasia, nucleated red cells

Features of EXTRAVASCULAR haemolysis

Direct Coombs (DAT) positive
– IgG and/or complement, IgA (rare)
– Antibodies detected at 37°C

30
Q

Warm Autoimmune Haemolytic Anaemia:

Treatment

A

Remove/treat the underlying cause

Corticosteroids

Intravenous immunoglobulin (IVIG/Polygam®)

Splenectomy

Immmunosuppression
– If steroids and/ or splenectomy have failed

Folic acid is given in severe cases

Blood transfusion
– Least incompatible
– If the specificity of the autoantibody is known, use donor blood that lacks the relevant antigen(s)

31
Q

Cold Autoimmune Haemolytic Anaemia

A

Antibody usually IgM and binds to red cells at 4°C

  • Highly effective fixing complement
  • INTRAVASCULAR AND EXTRAVASCULAR haemolysis

Antibody attaches to red cells in the peripheral circulation
– Blood temperature is cooled
– Antibody elute of cell at warmer parts and only
complement is usually detected

32
Q

Cold Autoimmune Haemolytic Anaemia:

Clinical Features

A

Chronic haemolytic anaemia:
– Aggravated by cold
– Mild jaundice and splenomegaly may be present

Acrocyanosis (purplish skin discoloration)
– Tip of the nose, ears, fingers and toes
– Agglutination of red cells in small vessels

33
Q

Cold Autoimmune Haemolytic Anaemia:

Laboratory Findings

A

Full blood count
– Normochromic/macrocytic anaemia
– Leucocytosis

Peripheral smear
– Haemagglutination
– Spherocytosis is less marked

DAT
– Complement (C3d) only on the red cell surface

High titre of “cold” autoantibodies to red cells

34
Q

Cold Autoimmune Haemolytic Anaemia:

Treatment

A

Keep the patient WARM
– Warmed fluids

Treating the underlying cause

Splenectomy doesn’t help
– Unless massive splenomegaly

Medication
– Immunosuppression

Steroids are not helpful

35
Q

Alloimmune Heamolytic Aneamia

A

Antibody produced when red cells of one individual reacts with red cell of another

36
Q

Alloimmune Heamolytic Anaemia:

Causes

A

Transfusion of ABO-incompatible blood

Rh disease of the new-born

Allogeneic transplantation

37
Q

Alloimmune Heamolytic Anaemia:

Laboratory Diagnosis

A

Full blood count and peripheral smear
– Anaemia
– Features of haemolysis-INTRA- AND/OR EXTRAVASCULAR

Direct antiglobulin test (Direct Coombs test)
– Positive

Antibody identification and quantification

38
Q

Drug Induced Heamolytic Aneamia:

Mechanism

A

Drug-red cell membrane complex

Drug-protein-antibody complex

True autoimmune haemolytic anaemia (Rare)

Haemolytic anaemia disappears once drug is stopped

39
Q

Drug-Red Cell Membrane Complex

A

Antibody directed against a drug-red cell membrane
complex

Only massive doses

Often antibiotics
– E.g. penicillin and ampicillin

40
Q

Drug-protein-antibody complex

A

Drug-protein-antibody complex

Deposition of complement
– E.g. quinidine, rifampicin

41
Q

True autoimmune haemolytic anaemia (Rare)

A

True autoimmune haemolytic anaemia

Role of drug uncertain
-E.g. methyldopa

42
Q

Infections

A

Causes haemolysis in a variety of ways:

  1. Precipitates an acute haemolytic crisis in G6PD deficiency
  2. Causes microangiopathic haemolytic anaemia
    • E.g. meningococcal or pneumococcal septicaemia
  3. Malaria causes haemolysis by extravascular destruction of parasitized red cells as well as by direct intravascular lysis
    -Blackwater fever is an acute intravascular haemolysis
    accompanied by acute renal failure caused by Falciparum malaria
  4. Clostridium perfringens septicaemia can cause intravascular
    haemolysis with marked microspherocytosis
43
Q

Red Cell Fragmentation Syndromes:

Definition

A

Physical damage to red cells due to:

  • Microangiopathic haemolytic anaemia (MAHA)
  • Abnormal surfaces
  • Mechanical trauma
44
Q

Microangiopathic haemolytic anaemia (MAHA)

A

– Red cells passing through abnormally small vessels
• Caused by deposition of fibrin strands or platelet
aggregates

45
Q

Abnormal Surfaces

A

Physical damage to red cells on abnormal surfaces
– e.g. artificial heart valves or arterial grafts
– Arteriovenous malformations

46
Q

Mechanical Trauma

A

March haemoglobinuria

47
Q

Microangiopathic Heamolytic Aneamia:

Clinical Presentation

A

Thrombotic microangiopathy

Pathological lesion on tissue biopsy
– Platelet-fibrin rich thrombus

48
Q

Microangiopathic Heamolytic Anaemia:

Causes

A

1.Primary thrombotic microangiopathy (TMA) syndromes:

Thrombotic thrombocytopenic purpura (TTP)

Haemolytic Uremic Syndrome (HUS)

  • Atypical HUS or Complement-mediated TMA
  • Shiga toxin-mediated HUS (ST-HUS)

Drug-induced TMA

2.Systemic disorders that may present with MAHA and thrombocytopenia:

Disseminated intravascular coagulation (DIC)

Systemic infection (Sepsis) : May be bacterial, viral, rickettsial, or fungal

Systemic malignancy

Pregnancy-related syndromes HELLP syndrome, pre-eclampsia, etc.

Severe hypertension

Systemic rheumatic diseases: E.g. Vasculitis, antiphospholipid syndrome, etc.

Haematopoietic stem cell or organ transplants

Renal vascular disorders

49
Q

Thrombotic Thrombocytopenic Purpura:

Types and Classification

A

Acquired TTP
– Severe ADAMTS13 deficiency (<10% ativity)
– Due to an ADAMTS13 antibody (autoimmune condition)

Hereditary TTP
– Inherited ADAMTS13 mutation

HIV associated TTP
– Exact pathogenesis uncertain

EMERGENCY REQUIRE URGENT TREATMENT AND REFERRAL

50
Q

TTP:

Diagnosis Types

A

Clinically Suspicion

Laboratory Suspicion

51
Q

Clinically Suspicion

A

MAHA
– Anaemia
– Fever

Platelet consumption
– Petechiae

Evidence of organ damage
– Neurological symptoms
– Cardiac symptoms
– Gastrointestinal symptoms

52
Q

Laboratory Suspicion

A

MAHA
– Red cell fragments (Schistocytes)
– Raised LDH +++

Platelet consumption
– Thrombocytopenia-Usually very low

Evidence of organ damage
– Renal dysfunction

53
Q

TTP

Pentad

A

video

54
Q

TTP:

Treatment

A

IMPORTANT!

Consider TTP in all patients with MAHA and thrombocytopenia - Especially if no alternative

Check peripheral smear, consult haematologist

Urgent referral to haematologist if TTP is suspected
– Infusion with Fresh Frozen Plasma
– Plasma exchange needed

Immunosuppression

55
Q

Other MAHA

A

Disseminated Intravascular Coagulopathy(DIC)

Pregnancy-Related Syndromes

56
Q

Disseminated Intravascular Coagulopathy(DIC)

A

Fibrin-rich microthrombi

Consumption of coagulation factors
– Leads to bleeding

Occasional red cell fragments

Thrombocytopenia less prominent

Abnormal coagulation screen

57
Q

Pregnancy-Related Syndromes

A

Patient pregnant

RED CELL FRAGMENTS on peripheral smear

HELLP syndrome
– Haemolysis
– Elevated Liver enzymes
– Low Platelets

Pre-eclampsia
– Neurological syndromes
– Proteinuria
– Hypertension

58
Q

Chemical and Physical Agents

A

Drugs

Wilson’s Disease

Chemical Poisoning

Severe Burns

  • Wilson’s disease
  • Chemical poisoning
  • Severe burns
59
Q

Drugs

A

E.g. dapsone and Salazopyrin®

High doses causes oxidative intravascular haemolysis with Heinz body formation in normal subjects

60
Q

Wilson’s Disease

A

Acute haemolytic anaemia

High levels of copper in the blood

61
Q

Chemical Poisoning

A

E.g. with lead, chlorate or arsine

62
Q

Severe Burns

A

Damage to red cells

Acanthocytosis or spherocytosis

Haematology (10 decks)

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