TB

Question 1

what is TB?

Answer 1

caseating granulomatous inflammation

It is a chronic infection described in many body sites - the lungs, gut, kidneys, lymph nodes, skin…

Question 2

describe the granulomas

Answer 2

they have a necrotic centre

surrounded by epitheliod cells and langerhans giant cells

you get the formation of Ghon focus

Question 3

what type of hypersensitivity reaction is it?

Answer 3

type 4 - granulomas with necrosis

Question 4

what factors affect the prevalence and risk of developing TB in the developed world

Answer 4

contact with high-risk groups

immune deficiency

lifestyle factors

genetic susceptibility

Question 5

what immune deficiency may case problems ?

Answer 5

HIV infection

corticosteroids or immunosuppressant therapy

chemotherapeutic drugs

nutritional deficiency (vitamin D)

diabetes mellitus

chronic kidney disease

malnutrition/body weight > 10% below ideal

if CD4 is low and ESR is high

Question 6

what lifestyle factors increase the risk?

Answer 6

drug/alcohol misuse
homelessness/hostels/overcrowding
prison inmates

Question 7

what happens when the mycobacteria enters the body

Answer 7

T-cell response to organism enhances macrophage ability to kill mycobacteria
this ability constitutes immunity

Question 8

what does the T cell response cause?

Answer 8

T-cell response causes granulomatous inflammation, tissue necrosis and scarring
this is hypersensitivity (type IV)

Question 9

what is the pathology of primary TB?

Answer 9

1st exposure and up to 5 years later it causes an infection

Question 10

what is the pathology of secondary TB?

Answer 10

reinfection or reactivation of disease in a person with some immunity

disease tends initially to remain localised, often in apices of lungs

can progress to spread by airways and/or bloodstream

Question 11

where does secondary TB tend to affect?

Answer 11

often in the apices of the lungs initially but can progress to spread by airways and/or bloodstream

Question 12

what tissue changes are indicated in primary TB?

Answer 12

small focus (ghon focus) in the periphery of the mid zone of lung

large hilar nodes (granulomatous) on the CXR

Question 13

what tissue changes are indicated in secondary TB?

Answer 13

fibrosing and cavitating apical lesions

much more necrosis and tissue damage at the site of infection

Question 14

what is an importatn diff. diagnosis for secondary TB?

Answer 14

cancer

Question 15

what are the features seen with latent infection?

Answer 15

• bacillli present in ghon focus
• sputum smear and culture negative
• tuberculin skin test usually positive
• CXR normal (small calcified ghon focus frequently visible)
• asymptomatic
• not infectious to others

Question 16

what are the features of active disease?

Answer 16

bacilli present in tissues or secretions

sputum commonly smear and culture positive in pulmonary disease
MTb can usually be cultured from infected tissue

Tuberculin skin test usually positive (and can ulcerate)

CXR shows signs of consolidation/ cavitatio/ effusion in pulmonary disease

symptomatic- night sweats, fever, weight loss and cough common

infectious to others if detectable in sputum

Question 17

what is the ratio of extra:intra pulmonary disease in latent TB?

Answer 17

55% pulmonary

45% extrapulmonary

Question 18

what are the respiratory symptoms of TB?

Answer 18

persistent productive cough (.3 weeks) and occasional haemoptysis

hoarseness

pleuritic pain

cough

haemoptysis

Question 19

what are the general symptoms of TB?

Answer 19

weight loss, night sweats, fever fatigue

Question 20

what are the meningeal symptoms of TB?

Answer 20

headache, drowsy, fits

Question 21

what are the GI symptoms of TB?

Answer 21

peritonitis, perforation, bowel obstruction, pain

Question 22

what are the signs of tb?

Answer 22

may hear upper zone crackles