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BDS2 HHD - Human Disease > 9. Haematology I: Clinical Aspects Of Haematological Disorders > Flashcards

9. Haematology I: Clinical Aspects Of Haematological Disorders Flashcards

1
Q

LOs

A
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2
Q

what is haematopoiesis?

A
  • the process through which all blood cells are derived
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3
Q

haematopoietic system composed of?

A
  • bone marrow
  • spleen
  • liver
  • lymph nodes
  • thymus
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4
Q

where does haematopoiesis occur?

A
  • It occurs in different sites depending on the individuals age:
    ~ Childhood = bone marrow of nearly all bones
    ~ Adults = axial skeleton and proximal parts of the long bones
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5
Q

what does haematopoiesis start with?

A

The process starts with a pluripotent stem cell, which is capable of both self-renewal and differentiation

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6
Q

Haematopoiesis progress (stem cells to mature cell lines)

A
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7
Q

Main Functions of Cell Lines:
- red blood cells
- neutrophils
- eosinophils
- basophils
- monocytes + macrophages
- platelets
- lymphocytes

A
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8
Q

red blood cells function

A

Transport O2 from lungs to tissues

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9
Q

neutrophils function

A

Chemotaxis, phagocytosis, killing of phagocytosed cells

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10
Q

eosinophils function

A

Neutrophil functions + antibody-dependent damage to parasites, immediate hypersensitivity

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11
Q

basophils function

A

Immediate hypersensitivity, modulate inflammatory response via proteases & heparin

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12
Q

monocytes + macrophages function

A

Chemotaxis, phagocytosis, killing of micro-organisms, antigen presentation and release of IL-1 & TNF

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13
Q

platelets function

A

Primary haemostasis (adhere to subendothelial connective tissue when exposed)

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14
Q

lymphocytes function

A

Immune response and haemopoietic growth factors

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15
Q

red blood cells indices
(normal haemoglobin values for diff ages)

  • Children 6mths – 6yrs
  • Children 6yrs – 14yrs
  • Adult males
  • Adult females
  • Pregnant females
A

Children 6mths – 6yrs 110 – 145 g/L
Children 6yrs – 14yrs 120 – 155 g/L
Adult males 130 – 170 g/L
Adult females 120 – 155 g/L
Pregnant females 110 – 140 g/L

*NOTE change in Hb units from g/dL to g/L
may be diff in older textbooks

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16
Q

Mean cell volume (MCV)

A

80 – 95 fL

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17
Q

what is anaemia?

A
  • Reduction in haemoglobin level below reference range for age and sex of individual
  • Rate at which anaemia develops dictates symptoms and signs
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18
Q

symptoms of anaemia

A
  • Symptoms:
    ~ Lassitude
    ~ Fatigue
    ~ Dyspnoea on exertion
    ~ Palpitations
    ~ Headache
    ~ Chest pain
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19
Q

signs of anaemia

A
  • Signs:
    ~ Pallor
    ~ Tachycardia
    ~ Wide pulse pressures
    ~ Systolic flow murmurs
    ~ Congestive cardiac failure
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20
Q

what are the classifications of anaemia?

A
  • mechanism of how it develops
  • morphology of how it develops
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21
Q

Classification – mechanism

A
  • Blood loss
  • Decreased red cell lifespan (haemolytic)
    ~ Congenital (sickle cell anaemia)
    ~ Acquired (malaria, drugs)
  • Impairment of red cell formation
    ~ Insufficient erythropoiesis
    ~ Ineffective erythropoiesis
  • Pooling and destruction in spleen
  • Increased plasma volume (pregnancy)
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22
Q

Classification – morphologies and common causes of these

A
  • Microcytic (decrease in size)
    ~ Iron deficiency
    ~ Thalassaemias

Normocytic
~ Acute blood loss
~ Anaemia of chronic disease
~ Chronic renal failure

Macrocytic (increase in size)
~ Alcoholism
~ Folate deficiency
~ Vitamin B12 deficiency
~ Drugs

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23
Q

What is iron deficiency anaemia?

A
  • Iron deficiency most common cause of anaemia worldwide
  • Excess iron potentially toxic so body tightly controls absorption
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24
Q

How does iron deficiency anaemia develop?

A
  • Develops via 3 mechanisms:
  1. Poor dietary intake (vegetarians and vegans)#
  2. Malabsorption (duodenum in Coeliac disease or jejenum in Crohn’s disease)
  3. Increased loss of iron through loss of red blood cells (commonly menorrhagia or gastrointestinal – peptic ulceration, inflammatory bowel disease, malignancy or hookworm infestation)
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25
Q

Manifestations of iron deficiency

clinical presentations

A
  • Mild deficiency typically asymptomatic
  • Classic presentation includes:
    ~ Koilonychia
    ~ Angular cheilitis
    ~ Atrophic glossitis
    ~ Recurrent oral ulceration
    ~ Burning mouth
    ~ Oesophageal web (Plummer-Vinson / Patterson-Brown Kelly Syndrome)
26
Q

management of iron deficiency anaemia?

A
  • Identify cause
  • Red flags include men and post-menopausal women (may have unexplained blood loss which may be associated with a malignancy)
  • Investigations:
    ~Blood film
    ~ Iron studies
  • Treatment:
    ~ Address underlying cause
    ~ Oral supplementation (ferrous sulphate 200mg
    x3/day for 3 months)
    ~ Parenteral available (fever, arthropathy,
    anaphylaxis)
    ~ Blood transfusion (only in severe compromise)
27
Q

What is normocytic anaemia?
associated with?

A
  • Anaemia’s of chronic disease
  • Associated with:
    ~ Chronic inflammatory / connective tissue
    conditions (rheumatoid arthritis)
    ~ Chronic infections (tuberculosis)
    ~ Chronic renal disease (due to reduction in
    erythropoietin)
    ~ Malignancies (bone marrow infiltration)
28
Q

what is Macrocytic anaemia divided into?

A

this is where you have the large RBCs

Divided into:

  1. Megaloblastic erythropoiesis - abnormal red cell development due to disordered DNA synthesis
  2. Normoblastic erythropoiesis – normal red cell maturation
29
Q

What is megaloblastic anaemia - folate?

A

folate deficiency

30
Q

what is folate used for?

derived from?

A
  • Folate essential for DNA synthesis
  • Derived from many food sources (especially green leafy vegetables)
31
Q

causes of megaloblastic anaemia - folate deficiency?

A
  • Causes of deficiency:
    ~ Inadequate intake (elderly, alcoholism)
    ~ Malabsorption (Coeliac disease, Crohn’s disease,
    resection)
    ~ Increased requirement (pregnancy, haemolytic
    anaemias, myelofibrosis)
    ~ Increased loss (dialysis, liver disease, congestive
    heart failure)
    ~ Drugs (methotrexate, phenytoin, trimethoprim)
32
Q

what is B12 used for?

derived from?

what does deficiency impact?

A
  • Vitamin B12 required in number of enzymatic reactions
  • Found only in foods of animal origin
  • Deficiency impacts on DNA synthesis
33
Q

causes of megaloblastic anaemia - vitamin B12 deficiency?

A

Causes of deficiency:
~ Inadequate intake
~ Inadequate secretion of intrinsic factor
(pernicious anaemia, gastrectomy)
~ Inadequate release from food (gastritis, PPI,
EtOH abuse)
~ Diversion of dietary B12 (bacterial overgrowth,
small intestinal strictures)
~ Malabsorption (Crohn’s disease, ileal resection)

34
Q

Clinical features of folate and B12 deficiencies

A

FOLATE & VITAMIN B12
- Generic symptoms & signs of anaemia
- Occasionally mild jaundice
- Glossitis
- Oral ulceration

VITAMIN B12
- Peripheral neuropathy (loss of proprioception and vibration sense) (nerve related damage) (typically periphery = fingers + toes)
- Demyelination with subacute combined degeneration of spinal cord (serious complication)
- Dementia

35
Q

management of megaloblastic anaemia?

A
  • Identify cause
  • Investigations
    ~ Blood film
    ~ Serum folate and B12 (*low B12 can lead to low
    folate – always test together)
  • Treatment
    ~ Address underlying cause
    ~ Oral supplementation (never folate only if B12
    level not known)
    ~ Parenteral vitamin B12 (IM) required in
    pernicious anaemia
36
Q

Normoblastic macrocytosis causes?

A
  • Alcohol excess
  • Liver dysfunction
  • Hypothyroidism
  • Drugs (methotrexate, azathioprine)
37
Q

Haemolytic anaemias
- in which there is a disruption in RBCs (haemolysis) is divided into?

A
38
Q

congenital haemolytic anaemias may be associated with?

A
  1. MEMBRANE DEFECTS
  2. ENZYME DEFECTS
  3. GLOBIN DEFECTS

EXTRA INFO

MEMBRANE DEFECTS
- Number of proteins essential to maintain cell membrane integrity
- Any mutation leads to increased fragility and haemolysis
- Hereditary spherocytosis most common congenital

ENZYME DEFECTS
- Glucose-6-phosphate dehydrogenase (G6DP) deficiency
- Involved in glucose metabolism
- Deficiency results in increased sensitivity to oxidative stress

39
Q

acquired haemolytic anaemia are divided into?

A
  • immune and non-immune causes

EXTRA INFO

IMMUNE
- occurs when IgG coated red cells interacting with marcophages resulting in phagocytosis
- Include autoimmune processes with antibodies against red cells (including idiopathic or secondary to infections, drugs, SLE, haematological malignancies)
- Alloimmune results from transfusion and production of antibodies to transfused red cell

NON-IMMUNE
- Include mechanical trauma (metallic valves), burns, infections (malaria) or drugs (dapsone)

40
Q

Clinical features of haemolytic anaemia?

A
  • Vary greatly depending on cause
  • Common features include:
    ~ Pallor
    ~ Jaundice (due to elevated bilirubin)
    ~ Splenomegaly
    ~ Expansion of erythropoiesis leading to bone
    deformities (frontal bossing) and pathological
    fractures
41
Q

Haemoglobin (Hb) normal structure?

A
  • Normal Hb comprises of 2 alpha and 2 beta chains
  • Each globin group is associated with a haem group (protoporphyrin ring and iron)
  • Adult Hb composition
    ~ Hb A (α2β2) 97%
    ~ HbA2 (α2δ2) 1.8-3.6%
    ~ HbF (α2γ2) <1.5%
42
Q

main function of Hb?

A
  • Fundamental role of O2 transportation
  • Hb undergoes conformational change between O2 bound and unbound states
  • Altering affinity for O2 (loads O2 in high O2 tension environment and releases in low)
43
Q
  1. what is thalassaemia?
  2. main groups?
  3. what does severity depend on
  4. what is used to diagnose thalassaemia
A

1

  • Common genetic disorder with significant associated morbidity and mortality
  • Excess chains precipitate in precursor red cells leading to premature death
  • Precipitated chains also result in oxidative damage to the cell membrane leading to haemolysis

2

  • 2 main groups depending on whether α or β chain defect
    ~ α-Thalassaemia
    ~ β-Thalassaemia

3

  • Severity depends on degree of globin chain imbalance

4

  • Diagnosis made on Hb electrophoresis (to identify various chains present in individual)
44
Q

α-Thalassaemia

  1. where most common
  2. prevalence?
  3. structure/ cause?
A
  1. Most common SE Asia (Thailand, Indonesia) and W Africa

2.
Prevalence 20-30%

  1. 4 α-globlin genes on 2 chromosomes
    - depending on number of genes affected, affects the severity?

a) α+-thalassaemia trait (deletion of 1 gene) – asymptomatic with normal Hb and reduced MCV

b) α0-thalassaemia trait (deletion of 2 genes on 1 chromosome) – slight reduction Hb and reduced MCV

c) Hb H disease (deletion of 3 genes) – chronic haemolytic anaemia however transfusion independent

d) Hb Bart’s hydrops fetalis syndrome (deletion of all 4 genes) – intrauterine or neonatal death

45
Q

β-Thalassaemia

  1. carriers % in world pop?
  2. most common where + prevalence
  3. why does it occur?
A

1.
~1.5% world population are β-thalassaemia carriers

2.
Southern Europe 10-30% especially Greece

3.
- Usually due to mutation rather than deletion affecting β-gene
a) Heterozygous β-thalassaemia (trait) –
asymptomatic
b) Homozygous β-thalassaemia – moderate to
marked anaemia developing within 1st 2 years
(may be transfusion dependent)

46
Q
  1. what do clinical classifications depend on?
  2. clinical classification of thalassaemia?
A

1.
- depends on the degree of anaemia seen
- based on minor or major presentation

2.
- Thalassaemia minima
~ Presence of mutation without clinical
consequence

  • Thalassaemia minor
    ~ Microcytosis and hypochromic red cells
  • Thalassaemia intermedia
    ~ Microcytic hypochromic anaemia
    ~ Extramedullary haematopoiesis with
    splenomegaly
  • Thalassaemia major
    ~ As above with severe anaemia and
    transfusion dependent
47
Q
  1. Clinical presentations of thalassaemia
  2. dental relevance?
A

1

  • Typically those of anaemia unless severe
  • If untreated leads to growth retardation, splenomegaly and bony deformities due to marrow expansion

2
ORAL
- Enlargement of maxilla (chipmunk facies)

  • Migration and spacing of upper anterior teeth
  • Main concern = iron overload due to transfusion leading to iron accumulation in myocardium (cardiac failure), liver (cirrhosis), pancreas (DM) and salivary glands
48
Q
  1. what is HbS?
  2. what causes it?
  3. where is prevalence highest?
A

1
Most common structural variant of Hb is HbS

2
- Due to mutation in β-globin gene
- Interaction of sickle β-globin chains with normal α-globin chains = HbS
- Results in deformation of cell into sickle shape

3
- Prevalence greatest in tropical Africa, Middle East and southern India
- Areas in which falciparum malaria is endemic

49
Q

sickle cell trait occurs in?

A
  • Occurs in Heterozygotes (20-40% HbS & remaining HbA)
  • Usually asymptomatic
  • Rarely experience spontaneous haematuria
50
Q

Sickle cell anaemia occurs in?

Clinical manifestations?

Sickling?

A
  • Homozygotes (100% HbS)
  • Clinical manifestations
    ~ Chronic haemolytic anaemia (60-90 g/L)
    ~ Hyposplenism (due to infarcts = increased risk
    of infection)
    ~ Splenic sequestration
    ~ Acute chest syndrome
    ~ CVA / TIA
    ~ Bone infarction and subsequent infections
    ~ Chronic leg ulcers
    ~ Haematuria and chronic renal disease

Sickling
~ shortened erythrocyte survival
~ microcirculation obstruction

51
Q

sickle cell anaemia management?

A
  • Diagnosed with Hb electrophoresis
  • Transfusion when necessary
  • Pneumococcal, Hib (Haemophilus influenzae type b) and meningococcal vaccinations (increased susceptibility due to hyposplenism)
  • Prophylactic penicillin

CRISES
- Acute vaso-occlusive painful episodes
- Precipitated by infection, dehydration, hypoxia
- Oral and IV fluids
- Analgesics (opiates)

52
Q

Why do transfusion reactions occur?

A

BLOOD GROUP DIFFERENCES
- due to the Variation in surface constituents of red cells can lead to immunological reaction between donor and recipient
- 30 major blood group systems
- Most important ABO and Rh systems
- Compatibility or cross-matching essential

53
Q

ABO

A
  • H antigen is attached to cell membrane
  • Presence of A or B allele lead to H antigen modification whereas O encodes for no modification

6 possible genotypes
~ AA
~ AB
~ AO
~ BB
~ BO
~ OO

4 phenotypes
~ A (can receive A or O)
~ AB (can receive A, B or O)
~ B (can receive B or O)
~ O (can only receive O)

54
Q

Rh

A
  • More complex than ABO
  • Encoded by 2 genetic loci on one chromosome (RHD and RHCE)
  • D antigen in most clinically relevant
  • RhD-negative person at significant risk of developing anti-D antibodies after transfusion of RhD-positive blood
  • Main relevance is to pregnant RhD-negative mothers
  • Fetus may be RhD-postive and placental transfer may lead to an adverse reaction
  • Pregnant women have Rh status tested and antenatal anti-D prophylaxis given if necessary
55
Q

Transfusion reactions

A
  • Immune-mediated transfusion reactions can be classified:

ACUTE REACTIONS
~occur within 24 hours of transfusion and include
acute haemolytic, febrile non-haemolytic,
allergic, and transfusion-related acute lung injury

DELAYED REACTIONS
~ occur days to weeks after the transfusion and
include delayed haemolytic transfusion
reactions, transfusion-associated graft-versus-
host disease and post-transfusion purpura

56
Q

clinical features of transfusion reactions

A

10% mortality

  • Fever
  • Agitation / anxiety
  • Rigor
  • Rash
  • Flushing and sweating
  • Chest / abdominal pain
  • Profound hypotension
  • Bleeding
  • Diarrhoea
57
Q

Management of transfusion reactions

A
  • Stop transfusion
  • Check patient identity against donor blood product unit
  • Replace giving set
  • Paracetamol
  • IV fluids
  • If suspect anaphylaxis IM Adr
  • Contact Haematology
58
Q

dental relevance of anaemia

A
  • May present with oral features suggestive of anaemia
  • Alternatively anaemia may complicate treatment
  • Without a clear explanation it may be sensible to delay treatment
59
Q

oral features of Haematinic deficiencies (iron, vitamin B12 and folate)

A
  • Angular cheilitis
  • Glossitis
  • Oral ulceration
  • Peripheral neuropathies
60
Q

oral features of Sickle cell

A
  • Oral pain possibly due to infarction
  • Osteomyelitis
  • Trigeminal neuropathy (due to osteomyelitis)
  • Hypomineralised dentition
61
Q

oral features - radiographic features

A
  • Dense lamina dura
  • Hypercementosis
  • Radio-opacities due to previous infarcts
62
Q

Treatment issues

A

BLEEDING
- If bone marrow infiltration there may be failure of other cell lines including platelets with increased risk of bleeding
- Liver disease may result in anaemia as well increased risk of bleeding due to impact on clotting factors synthesis

ANAESTHESIA
- Avoid prilocaine (methaemoglobinaemia)
- Thalassaemia and sickle cell anaemia can complicate procedures performed under general anaesthesia

BDS2 HHD - Human Disease (21 decks)

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