International Health - 201

Question 1

What bacterium is responsible for most cases of TB? What bacterium can cause TB in cattle?

Answer 1

Mycobacterium tuberculosis

M. bovis

Question 2

What is TB (in basic terms)?

Answer 2

A chronic bacterial infection

Question 3

Where is the greatest disease burden of TB in the world?

Answer 3

S.E. Asia

Question 4

Name 4 factors that increase TB transmission

Answer 4

1) MDR strains emerging
2) Poor national TB control programmes
3) Worsening socio-economic conditions
4) HIV incidence increasing suscepitibility

Question 5

Describe the microbiology of TB (shape, O2 preference, cell wall, growth rate)

Answer 5

Non-motile rod-shaped.
Obligate aerobe
Slow growing (grows on Lowenstin Jensen medium)
Peculiar cell wall - peptidoglycan and complex lipids

Question 6

How many people (%) exposed to TB actually develop the infection? Give 2 reasons that could explain this

Answer 6

10-30%
It could be that most people either inhale too few bacilli or that their immune system is sufficient to fight off the infection

Question 7

What factors increase the risk of developing TB if exposed?

Answer 7

Factors of impaired immunity such as; extremes of age, malnutrition, HIV/AIDS

Question 8

After inhalation where do TB bacilli settle?

Answer 8

In the alveoli - this causes local inflammation of the lung parenchyma

Question 9

What is the primary focus? (referring to TB)

Answer 9

TB bacilli settling in the alveoli and causing local inflammation. Usually occurs in upper lobes

Question 10

What forms the primary complex/Ghon complex? (referring to TB)

Answer 10

The primary focus together with enlarged lymph nodes

Question 11

Describe how the immune system can result in TB being latent

Answer 11

If the immune system manages to ‘wall off’ the primary complex TB is latent and can be reactivated later. This person is infected with TB but does NOT have the disease and cannot spread TB

Question 12

Can a person with latent TB spread the disease? What would their Mantoux test show?

Answer 12

No they cannot spread it as they do not have the active disease. Their mantoux test will be positive

Question 13

After inhaling TB bacilli there are 4 possible outcomes - what are they?

Answer 13

1) NO infection - this happens in 70-90% of people
2) Primary lung complex only - patient not unwell, cannot transmit disease
3) Pulmonary disease - patient unwell and can transmit disease
4) Systemic disease - patient unwell and can transmit disease

Question 14

What might happen in a patient with clinical hypersensitivity to M. tuberculosis? (This is a minority of people only)

Answer 14

Erythema nodosum and phlyctenular keratoconjunctivitis

Question 15

Name some general symptoms of TB

Answer 15

Fever, weight loss, night sweats, malaise

Question 16

Name some organ specific symptoms of TB

Answer 16

Lungs - chronic cough, productive, haemoptysis

CNS - TB meningitis, tuberculoma

Question 17

What is Pott’s disease?

Answer 17

TB affecting the spine. It is most common in children and presents as a swelling on the back.

Question 18

How is TB diagnosed?

Answer 18

Detailed history, CXR, AFB stain. PCR can be used when a result is needed quickly

Question 19

How is TB treated?

Answer 19

Long course of treatment - can cause reduced compliance.
DOTS - daily observed administration, shorter course.
Drugs are: Isoniazid, Rifampicin, Pyrazinamide, Ethambutol

Question 20

What is the definition of anaemia?

Answer 20

A reduction in the Hb in the blood, below normal range for age and sex.
Males - 13.5g/dL
Females - 11.5g/dL

Question 21

What is erythropoiesis?

Answer 21

The process of erythrocyte (RBC) production.

Question 22

Give a basic summary of erythropoiesis

Answer 22

• Epo is synthesized for cells of the renal cortex in response to tissue hypoxia.
• Epo stimulates stem cells within the bone marrow to differentiate into erythroid precursors, it induces RBC maturation

Question 23

What chronic disease can result in anaemia due to reduced RBC production?

Answer 23

Chronic renal disease. This is because Epo is produced predominantly by the kidney. A reduction in the production of Epo results in anaemia

Question 24

What morphology will anaemia due to Epo deficiency be?

Answer 24

Normocytic

Question 25

What is thalassaemia? What clinical signs might be seen in a child with this condition?

Answer 25

A form of chronic haemolysis - autosomal recessive blood disorder. Patients have reduced synthesis of either alpha or beta globin chains of Hb and make less Hb. Causes microcytic anaemia Frontal bossing

Question 26

What are haematinics?

Answer 26

Key micronutrients needed for a RBC and Hb to develop normally. They are IRON, VITAMIN B12 and FOLATE and are normally provided in a balanced diet.

Question 27

What is the rate-limiting step for erythropoiesis?

Answer 27

Hb concentration in the developing RBC

Question 28

What is the morphology of iron deficiency anaemia and why is this?

Answer 28

Microcytic and hypochromic (reduced Hb) anaemia. | This is because the RBCs divide more than normal, resulting in smaller cells.

Question 29

If someone has a Vitamin B12 or folate deficiency what kind of anaemia will they have and why?

Answer 29

Macrocytic anaemia. This is because these nutrients are important for DNA synthesis. A patient that is deficient will have reduced division of their RBCs resulting in larger cells that might be misshapen.

Question 30

Name 4 causes of iron-deficiency

Answer 30

- Poor intake (e.g. in the elderly, vegetarian, anorexic) - Reduced absorption (e.g. Crohn's, IBD, chronic diarrhoea) - Increased losses (e.g. menstruation, haemolysis) - Increased demand (e.g. pregnancy, breast feeding)

Question 31

Where is vitamin B12 absorbed?

Answer 31

Stomach and terminal ileum. Dietary B12 binds with intrinsic factor - the B12-IF complex is absorbed by the distal ileum

Question 32

Does vitamin B12 deficiency develop quickly or slowly? Why?

Answer 32

Slowly - it can take years to develop as the body has sufficient stores

Question 33

What is happening in pernicious anaemia?

Answer 33

IgG autoantibodies target gastric parietal cells and intrinsic factor. This results in a reduction in the secretion of IF.

Question 34

What 4 proteins are involved in the erythrocyte membrane? What happens if they are absent/mutated?

Answer 34

Spectrin, actin, protein 4.1 and ankyrin. Inherited disorders of these proteins results in a poorly formed normocyte that gets destroyed -> can be a cause of haemolytic anaemia.

Question 35

If a patient has G6PD deficiency what happens when their RBCs are put under oxidative stress? Give an example

Answer 35

Haemolysis occurs when the cell is under ox. stress (e.g. infection, drugs). G6PD deficiency is X-linked and relatively common.

Question 36

Will the reticulocyte count be raised, lowered, or the same in an anaemic patient?

Answer 36

It will be elevated

Question 37

Why might some anaemic patients have jaundice?

Answer 37

Excess haemolysis results in excess bilirubin which causes jaundice.

Question 38

Name some clinical features of anaemia. Symptoms and signs.

Answer 38

Headache, SOB, palpitations, confusion, koiloncyhia (iron deficiency), atrophic glossitis (B12 & folate deficiency), angular stomitis (B12 & folate deficiency), dysphagia (iron deficiency), peripheral oedema, weakness, ETC!