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HUMAN HEALTH AND DISEASE > Haematology I: Clinical Aspects of Haematological Disorders > Flashcards

Haematology I: Clinical Aspects of Haematological Disorders Flashcards

1
Q

What is haematopoiesis and what does the process start with?

A

The process through which all blood cells are derived

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

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2
Q

What is the haematopoietic system composed of?

A

The bone marrow, spleen, liver, lymph nodes & thymus.

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3
Q

Where does haematopoiesis occur?

A

Depends on the individual’s age:

Childhood= bone marrow of nearly all bones

Adults= axial skeleton & proximal parts of the long bones

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4
Q

What are the main functions of the mature cell lines?

A

Red blood cells - Transport O2 from lungs to tissues

Neutrophils - Chemotaxis, phagocytosis, killing of phagocytosed cells

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

Basophils - Immediate hypersensitivity, modulate inflammatory response via proteases & heparin

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

Platelets - Primary haemostasis (adhere to subendothelial connective tissue

Lymphocytes -Immune response and haemopoietic growth factors

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5
Q

What are the normal red blood cell indices?

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
Mean cell volume (MCV): 80-95 fL

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6
Q

What is anaemia?

A

Reduction in haemoglobin level below reference range for age and sex of individual

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7
Q

What are some of the symptoms and signs of anaemia?

A

Symptoms:

Lassitude - a condition of weariness or debility
Fatigue
Dyspnoea on exertion - he sensation of running out of the air and of not being able to breathe fast or deeply enough during physical activity.
Palpitations -
Headache
Chest pain

Signs:
Pallor
Tachycardia
Wide pulse pressures
Systolic flow murmurs
Congestive cardiac failure

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8
Q

By what mechanisms can anaemia develop?

A

-Blood loss

-Decreased red cell lifespan (haemolytic)
-Congenital (sickle cell anaemia)
-Acquired (malaria, drugs)

-Impairment of red cell formation
I-nsufficient erythropoiesis
-Ineffective erythropoiesis

-Pooling and destruction in spleen

-Increased plasma volume (pregnancy)

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9
Q

How can the morphology of red blood cells be described?

A

Microcytic - commonly seen in Iron deficiency and Thalassaemias

Normocytic - commonly seen in Acute blood loss, Anaemia of chronic disease, Chronic renal failure

Macrocytic - commonly seen in Alcoholism, Folate deficiency, Vitamin B12 deficiency or
Drugs

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10
Q

What are the 3 main mechanisms by which iron deficiency can develop?

A

Poor dietary intake (vegetarians and vegans)

Malabsorption (duodenum in coeliac disease or jejunum in Crohn’s disease)

Increased loss (commonly menorrhagia or gastrointestinal- peptic ulceration, inflammatory bowel disease, malignancy or hookworm infestation)

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11
Q

What is the most common cause of anaemia worldwide?

A

Iron deficiency
(Excess iron is potentially toxic so the body tightly controls its absorption)

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12
Q

How does iron deficiency typically manifest?

A

Koilonychia - a deformity of the nails where the central portion of the nail is depressed and the lateral aspects of the nail are elevated.

Angular cheilitis - an inflammatory skin process of variable etiology occurring at the labial commissure, the angle of the mouth

Atrophic glossitis - characterized by the partial or complete absence of filiform papillae on the dorsal surface of the tongue.

Recurrent oral ulceration

Burning mouth

Oesophageal web (Plummer-Vinson/Patterson-Brown Kelly Syndrome

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13
Q

How do you manage iron deficiency in a patient?

A

Identify the cause and investigate by doing blood films & 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)

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14
Q

What are normocytic anaemias?

A

-The anaemias of chronic disease
-These can be associated with:
-Chronic inflammatory/connective tissue conditions (rheumatoid arthritis)
-Chronic infections (tuberculosis)
-Chronic renal disease (due to reduction in erythropoietin)
-Malignancies (bone marrow infiltration)

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15
Q

What can macrocytic anaemia be divided into?

A

Megaloblastic erythropoiesis- abnormal red cell development due to disordered DNA synthesis

Normoblastic erythropoiesis- normal red cell maturation

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16
Q

What are megaloblastic anaemias associated with?

A

Folate deficiency

folate is essential for DNA synthesis & is derived from many food sources

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17
Q

What are the possible causes of folate deficiency?

A

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 (DMARDs), phenytoin (medicine used to treat epilepsy), trimethopriman (antibiotic))

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18
Q

What is vitamin B12 required for and where is it found?

A

It’s required in a number of enzymatic reactions & its deficiency impacts on DNA synthesis
It’s found only in foods of animal origin

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19
Q

What are the possible causes of vitamin B12 deficiency?

A

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)

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20
Q

What are the clinical features of folate & vitamin B12 deficiency?

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)
-Demyelination with subacute combined degeneration of spinal cord
-Dementia

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21
Q

How do you treat folate & B12 deficiency?

A

Identify cause, and investigate by doing blood films & checking serum folate & B12 (low B12 can lead to low folate- always check together)

Treat by addressing underlying cause, give oral supplementation (never folate only if B12 level not known); parenteral vitamin B12 (IM) required in pernicious anaemia

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22
Q

What are some of the causes of normoblastic macrocytosis?

A

Alcohol excess
Liver dysfunction
Hypothyroidism
Drugs (methotrexate, azathioprine both are DMARDs)

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23
Q

How are haemolytic anaemias classified?

A

Congenital
1. Membrane defects:
-Number of proteins essential to maintain cell membrane integrity

-Any mutation leads to increased fragility and haemolysis

-Hereditary spherocytosis most common congenital

  1. Enzyme defects:
    -Glucose-6-phosphate dehydrogenase (G6DP) deficiency

-Involved in glucose metabolism

-Deficiency results in increased sensitivity to oxidative stress

Acquired
1. Immune:
-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

  1. Non-immune:
    -Include mechanical trauma (metallic valves), burns, infections (malaria) or drugs (dapsone - leprosy, skin disorders)
24
Q

What are the clinical features of haemolytic anaemias?

A

They vary greatly depending on cause but generally include:

-Pallor
-Jaundice (due to elevated bilirubin)
-Splenomegaly
-Expansion of erythropoiesis leading to bone deformities (frontal bossing) and pathological fractures

25
Q

What does adult Hb comprise?

A

Hb A (97%)
HbA2 (1.8-3.6%)
HbF (<1.5%)

26
Q

What is thalassaemia?

A

Common genetic disorder with significant associated morbidity and mortality

There are 2 main groups depending on whether it’s an alpha or beta chain defect

27
Q

What are the potential implications of thalassaemia and how is thalassaemia diagnosed?

A

-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

-Severity depends on degree of globin chain imbalance

-Diagnosis made on Hb electrophoresis

28
Q

What are the different forms of alpha-thalassaemia?

A

4 α-globlin genes on 2 chromosomes

  1. α+-thalassaemia trait (deletion of 1 gene) – asymptomatic with normal Hb and reduced MCV
  2. α0-thalassaemia trait (deletion of 2 genes on 1 chromosome) – slight reduction Hb and reduced MCV
  3. Hb H disease (deletion of 3 genes) – chronic haemolytic anaemia however transfusion independent
  4. Hb Bart’s hydrops fetalis syndrome (deletion of all 4 genes) – intrauterine or neonatal death
29
Q

Where is alpha-thalassaemia most common?

A

SE Asia (Thailand, Indonesia) & W Africa
Prevalence is 20-30%

30
Q

What are the forms of beta-thalassaemia?

A

Usually due to mutation rather than deletion affecting β-gene

  1. Heterozygous β-thalassaemia (trait) – asymptomatic
  2. Homozygous β-thalassaemia – moderate to marked anaemia developing within 1st 2 years (may be transfusion dependent)
31
Q

How many people are affected by beta-thalassaemia and where is it most common?

A

~1.5% of the world population are beta-thalassaemia carriers
Prevalent in Southern Europe (10-30%), especially Greece

32
Q

What are the clinical classifications of the different thalassaemias?

A

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

33
Q

What is the clinical presentation of someone with thalassaemia?

A

Typically similar to those of anaemia unless it’s severe

If untreated, it can lead to growth retardation, splenomegaly & bony deformities due to marrow expansion

Oral manifestations:

Enlargement of maxilla (chipmunk facies)

Migration and spacing of upper anterior teeth

34
Q

What is the main concern with a thalassaemia patient requiring transfusions?

A

Iron overload- the repeated tranfusions can lead to iron accumulation in myocardium (cardiac failure), liver (cirrhosis), pancreas (DM) & salivary glands

35
Q

What is the most common structural variant of Hb and how does it arise?

A

HbS
Due to mutation in beta-globin gene which then leads to an interaction of the sickle beta-globin chains with normal alpha-globin chains= HbS
This results in the deformation of cell into sickle shape

36
Q

Where is the prevalence of HbS greatest?

A

Prevalence greatest in tropical Africa, Middle East & southern India and areas where falciparum malaria is endemic

37
Q

In what kind of individuals does sickle cell trait occur?

A

Heterozygous individuals (20-40% HbS & remaining HbA)

38
Q

Do people with sickle cell trait have any symptoms?

A

They’re usually asymptomatic but can rarely experience spontaneous haematuria (presence of blood in urine)

39
Q

In what kind of individuals does sickle cell anaemia occur?

A

Homozygous individuals (100% HbS)

40
Q

What are the clinical manifestations of sickle cell anaemia?

A

-Chronic haemolytic anaemia (60-90 g/L)
-Hyposplenism (due to infarcts = increased risk of infection)
-Splenic sequestration
-Acute chest syndrome
-CVA / TIA
-Bone infarction & subsequent infections
-Chronic leg ulcers
-Haematuria & chronic renal disease

41
Q

What can sickling result in?

A

Shortened erythrocyte survival and microcirculation obstruction

42
Q

How do you manage sickle cell anaemia?

A

Diagnosed with Hb electrophoresis

Transfusion when necessary

Pneumococcal, Hib (Haemophilus influenzae type b) and meningococcal vaccinations (increased susceptibility due to hyposplenism)

Prophylactic penicillin

43
Q

How do you manage sickle cell anaemia crises, in which you have acute vaso-occlusive painful episodes?

A

It’s precipitated by infection, dehydration, hypoxia so:
Oral and IV fluids
Analgesics (opiates)

44
Q

How does a transfusion reaction come about?

A

Variation in surface constituents of RBCs can lead to immunological reactions between donor and recipient

Compatibility/cross-matching is essential for the transfusion to take place successfully otherwise you get reactions

45
Q

How does the ABO system work?

A

It relates to the H antigen attached to the cell membrane

The presence of either the A or B allele leads to H antigen modification whereas O encodes for no modification

46
Q

How many blood group systems are there and which ones are most important?

A

30 major blood group systems
The most important ones are the ABO and Rh systems

47
Q

What are the possible genotypes and phenotypes in the ABO system?

A

6 possible genotypes: AA, AB, AO, BB, BO, OO

4 possible 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)

48
Q

Describe the Rh system.

A

It’s more complex than ABO
It’s encoded by 2 genetic loci on 1 chromosome (RHD & RHCE)
The D antigen is the most clinically relevant, especially in pregnant women

49
Q

Why are immune-mediated transfusion reactions important to manage promptly?

A

Because they are associated with a 10% mortality rate

50
Q

Why is the D antigen most clinically relevant?

A

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

51
Q

How can immune-mediated transfusion reactions be classified?

A

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

52
Q

How do you manage the 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

53
Q

What is the dental relevance of all of these disorders?

A

They may present with oral features suggestive of anaemia

Alternatively, anaemia may complicate treatment

Without a clear explanation, it may be sensible to delay treatment

54
Q

What are some oral manifestations of haematinic deficiencies (iron, vitamin B12, folate) and sickle cell anaemia?

A

Haematinic deficiencies:
-Angular cheilitis
-Glossitis
-Oral ulceration
-Peripheral neuropathies

Sickle cell anaemia:
-Oral pain possibly due to infarction
-Osteomyelitis
-Trigeminal neuropathy (due to osteomyelitis)
-Hypomineralised dentition
(Radiographic features may also include dense lamina dura, hypercementosis, & radio-opacities due to previous infarcts)

55
Q

What are some other important treatment issues to consider as a dentist?

A
  1. Bleeding:
    -If there is a 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

  1. Anaesthesia:
    -Avoid prilocaine (methaemoglobinaemia)

-Thalassaemia and sickle cell anaemia can complicate procedures performed under general anaesthesia

HUMAN HEALTH AND DISEASE (58 decks)

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