TB only

Question 2

Scenario: a young indian lady came back from foreign travel with cervical lymphadenopathy (anterior triangle mass), loss of weight, night sweats.

What is the differential diagnosis?

Answer 2

-Hodgkin’s lymphoma (more in this age group and involves cervical lymph nodes more commonly)
-TB

Question 3

Scenario: a young indian lady came back from foreign travel with cervical lymphadenopathy (anterior triangle mass), loss of weight, night sweats.

Which labs will you send her sputum to?

Answer 3

-Microbiology and cytology labs

Question 4

What are the tests for TB?

Answer 4

-Sputum examination (culture, ziehl Neelsen stain)
-Mantoux test
-PCR to differentiate mycobacteria tuberculosis from other species
-QuantiFERON (interferon gamma assays)
-FNAC of lymph node

Question 5

How would you label the sputum specimen?

Answer 5

-Category-B UN3373 (infectious substance)

Question 6

Where would you put the sputum sample?

Answer 6

-In biohazard bag

Question 7

What organisms can cause TB?

Answer 7

-Mycobacterium tuberculosis
-Mycobacterium avium intracellulare (MAC)–> disseminated infection in immunocompromised patients
-Mycobacterium bovis

Question 8

What are the culture media for mycobacteria?

Answer 8

-Solid media: lowenstein jensen media, middlebrook media
-Liquid media: BACTEC/MGIT (mycobacteria growth indicator tube)

Question 9

How long would you culture the sputum?

Answer 9

-1-8 weeks

Question 10

What type of protein deposition would you get in TB?

Answer 10

Amyloid

Question 11

Given FNAC result: (necrotic tissue, histiocytes, giant cells), interpret?

Answer 11

TB

Question 12

What are giant cells? what are examples?

Answer 12

-Multinucelated cells comprising of macrophages often forming granuloma (e.g. langerhans giant cells, reed sternberg cells)

Question 13

What would the public health concerns be?

Answer 13

1. Notify the consultant in communicable disease control
2. Avoid working in a food factory
3. Use mask during sneezing or coughing
4. DOTS (directly observed treatment, short course) anti TB therapy
5. Contact tracing: the identification and diagnosis of persons who may have come into contact with an infected person

Question 14

What is your advice to contacts?

Answer 14

-Counselling, screening and treatment of other family members

Question 15

What is a granuloma?

Answer 15

Organised collection of macrophages fusing to form langerhans giant cells

Question 16

What are other causes of granuloma?

Answer 16

Infections
-Bacterial (TB, leprosy, syphilis, aspiration pneumonia)
-Parasitic infection (schistosomiasis_
-Fungal infections (Histoplasmosis)

Non infective causes
-Sarcoidosis
-Crohn’s disease
-Rheumatoid arthritis
-Foreign body

Question 17

What is the pathogenesis of TB?

Answer 17

1. Infection begins when mycobacteria reach the alveolar air sacs
2. Here they replicate within endosomes alveolar macrophages
3. Macrophage attempts to kill mycobacterium but cannot be killed by them due mycolic acid capsule: phagolysosome is ineffective
4. Primary infection site in the lung is the Ghon focus: can spread to distant sites from here haematogenously
5. Inflammatory cells (macrophages, epitheloid cells, T cells, b lymphocytes, fibroblasts) aggregate to form granulomas with caseous necrosis centrally
6. Multinucleate giant cells formed by macrophages

Question 18

What is a mycobacterium?

Answer 18

-Non motile
-Non-sporulating
-Usually aerobic
-Weakly gram positive (stains very weakly due to waxy cell wall but is genetically similar to gram +ve)
-‘acid fast’: have high content of mycolic acid in cell wall

Question 19

Where can TB affect in the body?

Answer 19

-Almost anywhere
-90% of cases in the lungs
-20% outside lungs to pleura/cns/lymphatics/GU system, etc

Question 20

-What is potts disease, in relation to TB?

Answer 20

-TB infection of the spine
-Occurs following haematogenous spread of TB, usually affecting lower thoracic/lumbar spine
-Progressive destruction of bones and intervertebral discs can cause spinal collapse/sharply angled spinal curvature
-Abscesses can form, which cause paraplegia secondary to cord compression or track down to psoas muscle

Question 21

What is miliary TB?

Answer 21

-Widely disseminated TB throughout the body
-Usually occurs following haematogenous dissemination, is characterised by distinctive pattern seen on CXR with large numbers of tiny opacities widespread throughout the lungs
-Miliary TB may also be found in liver/spleen/pancreas

Question 22

How is TB diagnosed?

Answer 22

Active TB:

-1. Fluid samples (sputum/bronchial-alveolar lavage) for acid fast bacilli using auramine-rhodamine or ziehl-nielsen staining

2. PCR to differentiate m tuberculosis from other mycobacteria and allow testing for multi drug resistance
3. CXR and CT chest (and other imaging modalities if looking for extra-pumonary TB)

Tests for latent TB:

1. Interferon gamma release assay e.g. quantiferon blood test. More reliable than mantoux
2. Immunological tests for latent TB include mantoux test or tuberculin skin test: a small amount of tuberculin is injected into forearm and presence of delayed hypersensitivity reaction is assessed at 48-72 hrs - a positive test can indicate latent TB/previous infection but it can be weakly positrive in people who have had the BCG and can be falsely negative in immunocompromised patients. Strong +ve test can mean active TB

Question 23

How is pulmonary TB treated?

Answer 23

-Multiple antibiotics:
–> rifampicin, isoniazid, pyrazinamide, ethambutol

Indications for surgery:
–> recurrent or massive haemoptysis
–> bronchopleural fistula
–> aspergilloma within tuberculous cavity
–> multidrug-resistant disease unresponsive to chemothgerapy

Question 24

What is a granuloma?

Answer 24

-Organised collection of macrophages, which can often fuse to form langerhans giant cells.
-The collection of macrophages is often surrounded by a rim of lymphocytes

Question 25

Lytic vs sclerotic bone mets

Answer 25

prostate
-sclerotic

mixed
-breast

lytic
-Breast
-thyroid
-renal cell