TB

Question 1

def

Answer 1

granulomatous disease caused by mycobacterium tuberculosis

primary - initial infection may be pulmonary (inhalation) or GI
miliary TB - when there is haematogenous dissemination
post-primary - when there is reinfection or reactivation

Question 2

what is haematogenous dissemination

Answer 2

spread through the blood

haematogenous dissemination causes miliary TB

Question 3

aetiology

Answer 3

mycobacterium tuberculosis is an intracellular organism (acid-fast bacilli) which survives after being phagocytosed by macrophages

Question 4

epi

Answer 4

annual mortality of 3m (majority in developing countries)
UK incidence is 6000PA
more common in asians

Question 5

history & examination of primary TB

Answer 5

mostly asymptomatic
fever, malaise
cough, wheeze
erythema nodosum (red lumps on the shins)

Question 6

history & examination of miliary TB

Answer 6

fever
weight loss
meningitis
yellow caseous tubercles which spread to other organs (bone & kidneys) and are dormant for years

Question 7

history & examination of post-primary TB

Answer 7

fever/nights sweats, malaise
weight loss
SOB, cough, sputum, haemopytsis
pleuritic chest pain
signs of pleural effusion
consolidation
fibrosis

Question 8

history & examination of non-pulmonary TB

Answer 8

common in immunocompromised

Question 9

history & examination of TB

Answer 9

1 lymph nodes
-suppuration (pus formation) of cervical lymph nodes which leads to abscesses or sinuses which discharge pus & spread to skin
2 CNS
-meningitis
-tuberculoma
3 skin
-lupus valgaris (dark red patches)
4 heart
-pericardial effusion
-constrictive pericarditis
5 GI
-obstruction
-change in bowel habit
-ascites
6 genitourinary
-UTI symptoms
-renal failure
-infertility
7 adrenal
-insufficiency
8 bone/joints
-osteomyelitis
-arthritis
-paravertebral abscesses * vertebral collapse (Potts disease)
-spine cord compression from abscesses

Question 10

what is potts disease

Answer 10

TB in the vertebrae

paraplegia (loss of motor & sensory function of lower extremities)

Question 11

investigations

Answer 11

1 sputum/pleural fluid/bronchial washings
-microscopy with a Ziehl-Neelson stain
-culture
2 tuberculin test
-positive in previous exposure to M. TB or BCG
-strongly positive may indicate current infection
3 mantoux test
-intradermal injection of PPD whichha causes a hardened red mass if positive
4 heaf test
-drop of PPD and observe papule size
5 interferon-gamma test
-in latent TB, exposure of host T cells to TB antigens causes release of interferon
-high specificity (negative with BCG vaccine) so can be used to diagnose latent TB if tuberculin test is positive
6 HIV testing

Question 12

what is PPD

Answer 12

purified protein derivative

Question 13

investigations - CXR

Answer 13

primary infection
-peripheral consolidation
-hilar lymphadenopathy
miliary
-fine shadowing
post-primary
-upper lobe shadowing
fibrosis & cavitation
-calcification
-pleural effusion
-hilar lymphadenopathy