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Human Disease > Haematology > Flashcards

Haematology Flashcards

1
Q

Define Haematopoiesis, Outline what areas of the body make up the Haematopoietic System and compare Childhood v Adult Haematopoiesis

A

The process via which all blood cells are produced is known as Haematopoiesis.
The process starts with a Haemocytoblast, which is a pluripotent stem cell capable of self -renewal and differentiation into 2 main cell lines (myeloid progenitor and lymphoid progenitor).The main 2 areas in an adult where this occurs is in the bone marrow of the axial skeleton and proximal parts of long bones and the spleen. In a child it will also occur more extensively in bone marrow of nearly all bones, as well as liver, thymus and lymph nodes, whose activity will become more/less important with age.

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2
Q

What are the two main measures taking in regards to RBCs and what are their healthy ranges?

A

Haemaglobin Levels. Adult male 130-170g/L. Less in women, and children, even less in pregnant women

MCV. This is the average volume of each RBC. Normal range is 80-95fL (femtolitres)

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3
Q

Define Anaemia.

A

Refers to any reduction in Haemaglobin levels below the reference range for the age and sex of the individual.

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4
Q

Outline the main general Signs/Symptoms of Anaemia.

What does the severity if them tell us?

A 
Symptoms:
Lassitude + Fatigue
Breathlessness on exertion
Palpitations
Headaches
Chest Pain
Signs
Pallor (seen on FOM and conjuctiva)
Tachychardia
Wide pulse pressures
Flow murmurs
Congestive cardiac failure (late sign)

Fewer and less severe s/s a patient has, the slower the progression and the more subtle their anaemia likely is.

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5
Q

What are the 5 classifications of anaemia by mechanism?

A
  1. Sufficient Blood Loss
  2. Haemolytic RBCs (may be congenital i.e. sickle cell anaemia or acquired i.e. malaria/drug induced)
  3. Insufficient/Ineffective Erythropoiesis
  4. RBC pooling and destruction in Spleen
  5. Physiological anaemia (i.e. in pregnancy plasma volume increases on a larger scale than RBCs leading to ‘haemodilution’ and anaemia.
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6
Q

What is the classification by morphology and give MCV ranges for each.

A

Microcytic anaemia MCV<80

Normocytic anaemia, normal MCV

Macrocytic anaemia MCV>95

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7
Q

What are the two common causes of Microcytic Anaemia?

A

Fe deficiency anaemia and Thalassaemias

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8
Q

Why does body tightly control Fe absorption?

What are the 3 main mechanisms by which Fe deficiency anaemia occurs giving examples?

A

Because Fe in excess is potentially toxic

Insufficient dietary intake (vegans/vegetarians lol)

Malabsorption (i.e. in duodenum due to coeliac disease)

Increased loss (commonly mennorhagia in or GI causes-peptic ulceration, IBD, hookworm)
But don't be satisfied with these reasons as Malignancies also a major cause of unexplained Fe defiency anaemia.
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9
Q

Main s/s of Fe deficiency anaemia?

A

Those with mild deficiency will be asymptomatic

More severe/faster progressing cases will have:

Koilonychia (thin spoon shaped nails)

Orally:
Angular Cheilitis
Atrophic Glossitis (atrophy of lingual papillae leaving smooth tongue, tender and painful.
Recurrent ulceration
Burning mouth

Oesophageal Web

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10
Q

Outline the management and treatment for Fe deficiency anaemia?
Who are the red flag patients?

A

In managing: first try and identify the cause.
Red flag patients are 50+ men and post-menopausal women with unexplained Fe- def’ anaemia

When treating, adress underlying cause.
Give oral supplementation of Ferrous sulphate 200mg TDS for 3/12 the reassess.
If necessary, parenteral administration available.

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11
Q

What is Thalassemia?

How is it diagnosed?

A

Common genetic disorder which affects the alpha or beta chain structure of Hb.
Diagnosed by Hb Electrophoresis.

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12
Q

Compare alpha and beta thallasemia in terms of geographic prevalence. What happens to the genes?

A

Alpha seen in SE asia and w africa. Deletion of alpha-globin genes. The more are deleted, the more severity increases from mild MCV reduction to in utero/neonatal death. Deletion of 2 or less genes is considered a trait. 3/4 is considered disease.

Beta thalassaemia is seen more commonly in southern europe especially Greece.
Due to gene mutation. Heterozygous trait will be asymptomatic. Homozygous sufferer will have moderate/marked anaemia which develops from 0-2 yrs of age.

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13
Q

Outline the 4 stage clinical classification Thalassaemia

A

Minima-presence of genetic disorder. No clinical consequence

Minor- RBCs microcytic and hypochromic

Intermedia- as above plus extramedullary haematopoiesis and sphlenomegaly

Major- as above plus severe anaemia and transfusion dependency

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14
Q

What are the clinical presentations seen in severe thalassaemia?

How would a skull x-ray appear?

What is the main concern in a transfusion dependent patient?

A

Untreated th’ leads to growth retardation, sphlenomegaly and bony deformities due to marrow expansion.

Patient will have enlarged maxilla (chipmunk face)
Spaced out upper anterior teeth.
Skull X-ray would show: Hairs on end appearance
Delayed pneumatisation of maxillary sinuses and ‘chickenwire’ appearance of alveolar bone.

Main concern is iron overload leading to Fe accumulation in myocardium, liver, pancreas and salivary glands.

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15
Q

What are the main causes of Normocytic anaemia?

A

Acute blood loss, chronic inflammation/infection/renal disease, malignancies

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16
Q

How does chronic inflammation/infection/renal disease cause Normocytic Anaemia?

A

Infection/Inflammation/Disease cause immune system to make 4 main changes.

  • It makes the use and storage of iron less efficient.
  • It can cause the kidneys (especially in anaemia due to chronic renal disease) to produce less erythropoietin (EPO) hormone require to signal process in bone marrow.
  • the bone marrow can respond abnormally to EPO
  • lastly RBCs themselves can become haemolytic and die at a faster rate than they are replenished.
17
Q

Macrocytic Anaemia can be divided into what two groups based on Erythropoiesis?

A

Megaloblastic erythropoiesis where disordered DNA synthesis leads to abnormal RBC development.

Normoblastic erythropoiesis where everything is normal up till point of maturation. i.e.. blast is normal.

18
Q

Why do we need folate?

What are the 5 causes of folate deficiency leading to normocytic anaemia?

A

Folate is essential for DNA synthesis

Deficiency causes inc:

Inadequate intake

Malabsorption (coeliac disease, jejunum resection)

Increased requirement (pregnancy, haemolytic anaemias)

Increased loss (liver disease, dialysis)

Drugs (methotrexate, this is an immunosuppressant drug which causes increased folate excretion, so folic acid normally prescribed alongside it. Phenytoin)

19
Q

Why is Vitamin B12 required in the diet?
In what foods is it found?

What are the causes for its deficiency?

A

Required in number of enzymatic reactions and deficiency impacts DNA synthesis.
It is only found in foods of animal origin (meat, milk, eggs).

Deficiency caused by:

  1. Inadequate Intake
  2. Inadequate Intrinsic Factor Secretion (required for B12 secretion), due to AI disease against parietal cells/IF or resective surgery. If this occurs will get a pernicious anaemia where parenteral B12 administration would be required
  3. Inadequate release from food (gastritis, PPIs, Alcoholism)
  4. Diversion of dietary B12 from desired pathway (bacterial overgrowth, small intestinal anaemia)
  5. Malabsorption (crohn’s, ileum resection
20
Q

Outline the clinical features of folate and B12 deficiencies

A

For both, get Generic anaemia s/s, occasionally mild jaundice, glossitis + oral ulceration.

In addition to these, for B12 also get peripheral neuropathy and demyelination with subacute combined degeneration of spinal cord.

21
Q

Management of Megaloblastic anaemias (folate/b12 deficiency)

A

Management of these megaloblastic anaemias should include investigations to identify cause. A blood film, followed by serum folate and B12 testig should be done. When doing serum testing, it is important to take the B12 and Folate sample together, reintroduce it together, and even when giving supplements, give both together, as not doing this can lead to neurological damage (grey are not yet fully understood).

If anaemia is pernicious, require parenteral B12 supplementation to bypass GI system i.e. intramuscular injection

22
Q

Causes of Normoblastic Anaemia

A
  1. Excess Alcohol
  2. Liver Dysfunction
  3. Hypothyroidism
  4. Drugs
23
Q

Outline the 3 congenital defect types which result in haemolytic anaemias

A

Membrane Defects- mutation which affects number of proteins essential to maintain cell membrane integrity leads to fragility and haemolytic of them. Hereditary spherocytosis (sphere shaped RBCs) is an example

Enzyme Defects- G6DP Deficiency results in increased sensitivity to oxidative stress

Globin Defects-includes thalassaemias and sickle cell anaemia

24
Q

Outline the two types of acquired causes of haemolytic anaemias

A

Cause will either be immune or non-immune.

Immune causes can either be autoimmune (RBCs become coated in IgG and get phag’d by Macphag’) or
Alloimmune cases can occur following transfusion of RBCs triggering an antibody production against them.

Non-immunes causes include mechanical trauma (i.e. metallic valve placement), burns, infections, drugs

25
Q

Clinical Features of Haemolytic Anaemias

A

Depends greatly on cause. Apart from generic s/s of anaemia also may get.
Jaundice
Sphlenomegaly, i.e. an enlargement of the spleen causing a reduction in no of all blood cells which in turn leads to a compensatory proliferative response by bone marrow to increase erythropoiesis but which itself can lead to bone deformities (such as frontal bossing) and pathological fractures

26
Q

Describe the structure of Haemoglobin and how it is adapted to its role in loading/unloading oxygen.

A

Hb has the fundamental role of O2 transportation. Normal Hb (known as HbA) will be made up of 2 alpha and 2 beta chains which form a ring associated with a Fe molecule. O2 bound and unbounded Hb will have different structures achieved by conformational changes. This is important in allowing Hb to alter its oxygen affinity in different circumstances (low affinity in low oxygen areas, i.e. so can unload at tissue sites, and high affinity in high oxygen areas, i.e. so can ‘load’ at lungs). Adult Hb is 97% of the structure described at start of paragraph. 2 other types exist, just be aware of this that’s enough.

27
Q

What is sickle cell anaemia?
What makes it occur?
What morphological effect does this have on the RBC?

A

HbS is a common structural variant of Hb where due to a mutation in the beta global chain gene, RBCs with a mutated beta chain have a sickle shaped

28
Q

Compare sickle cell trait to sickle cell anaemia in terms of clinical manifestation

What is sickling? What does it cause?
How is sickle cell anaemia managed?

A

Those with sickle cell trait (heterozygous) are usually asymptomatic. May experience spontaneous haematuria.

Homozygotes will have chronic haemolytic anaemia. Hb count 60-90.

Sickle cells often perform sickling, this is shortened erythrocyte survival and microcirculation obstruction leading to clotting and clumping of RBC leading to a number of issues via the infarcts (localised tissue death due to lack of blood supply to certain areas) that they cause. These incuse hyposplenism, acute chest syndrome, stroke, bone infarction. Infarcts lead to increased chance of infections in the areas they are located at, therefore management of px normally involves pneumococcal, Hib and meningococcal vaccinations and prophylactic penicillin. This and all other management measures are generally supportive measures in order to avoid a sickle crisis occurring. This is an acute painful vaso-occlusive episode. It is followed by localised infection, dehydration and hypoxia where it occurs and must be treated via hospital administration where oral and IV fluids can be given and large doses of analgesic opiates can be given.

29
Q

outline the ABO system of blood grouping

A

ABO system involves type of modification, if any of H antigen on RBC. A allele gives A modification, B allele gives B modification and O allele gives no modification.
A and B are dominant over O, when A and B both present, person will be AB, otherwise A, B or O. O is universal donor, AB is universal recipient.

30
Q

Outline the Rh system of blood grouping.

Describe the relevance to pregnant mothers

A

Rh system is encoded by 2 genetic loci which are found on one chromosome, (RhD and RhCE). The D antigen part is the most important. An RhD negative person given RhD positive blood caries the risk of them producing antibogy to D antigen and rejecting donation.
Clinically the main relevance is with pregnant RhD negative mothers. If they are neg but fetus is RhD positive, there is a risk that placental transfer of RhD from child to mother, triggering D-antigen antibody in mother, which to her will be of no consequence, but to child will act against him/her. Therefore, pregnant women who are RhD negative are given antenatal anti-D prophylaxis ( contains anti-D IG to neutralise any RhD positive antigens to neutralise them before antibodies to them can be produced) to ensure that if what described above does happen, they won’t produce antibody to go on and affect a RhD positive child.

31
Q

What are the two types of immune mediated transfusion reactions and what do they include?

A

Reactions to transfusions can be split into acute and delayed.

Acute reactions include acute haemolytic, allergy, and transfusion related lung injury and occur within 24 hours of transfusion

Delayed reactions include haemolytic reactions, graft v host disease and purpura and occur in days to weeks after transfusion.

32
Q

What is the mortality rate for an acute transfusion reaction?
What are the 4 main clinical features and outline management

A

10%

Fever, Rash, Flushing + sweating, Profound hypotension.

Stop transfusion and double check patient ID against blood donor. Replace all apparatus.
Give paracetamol and IV fluid for patient comfort.
If suspect allergic response administer intramuscular adrenaline.
Contact Haematology.

33
Q

What is the dental relevance of aneamia?

How may it complicate treatment?

A

Be aware of oral features

May give increased infection risk

34
Q

What are the oral features of haematinic deficiencies (folate/b12/iron)?
What are the oral and radiographic features of sickle cell anaemia?

A

Angular cheilitis
Glossitis
Oral ulceration
Peripheral neuropathies (burning mouth)

Sickle cell
Infarct related oral pain
Osteomyelitis (–> trigeminal neuropathy)
Hypomineralised dentition

Rx- Dense lamina dura, Hypercementosis, Radiopacities due to previous infarcts

35
Q

What treatment issues are associated with anaemia in terms of anaesthesia?

A

Avoid Prilocaine

Avoid GA for thalassaemia and sickle cell pts as increase in oxidative stress can trigger a crisis

Human Disease (4 decks)

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