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?
-Hodgkin’s lymphoma (more in this age group and involves cervical lymph nodes more commonly)
-TB
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?
-Microbiology and cytology labs
What are the tests for TB?
-Sputum examination (culture, ziehl Neelsen stain)
-Mantoux test
-PCR to differentiate mycobacteria tuberculosis from other species
-QuantiFERON (interferon gamma assays)
-FNAC of lymph node
How would you label the sputum specimen?
-Category-B UN3373 (infectious substance)
Where would you put the sputum sample?
-In biohazard bag
What organisms can cause TB?
-Mycobacterium tuberculosis
-Mycobacterium avium intracellulare (MAC)–> disseminated infection in immunocompromised patients
-Mycobacterium bovis
What are the culture media for mycobacteria?
-Solid media: lowenstein jensen media, middlebrook media
-Liquid media: BACTEC/MGIT (mycobacteria growth indicator tube)
How long would you culture the sputum?
-1-8 weeks
What type of protein deposition would you get in TB?
Amyloid
Given FNAC result: (necrotic tissue, histiocytes, giant cells), interpret?
TB
What are giant cells? what are examples?
-Multinucelated cells comprising of macrophages often forming granuloma (e.g. langerhans giant cells, reed sternberg cells)
What would the public health concerns be?
- Notify the consultant in communicable disease control
- Avoid working in a food factory
- Use mask during sneezing or coughing
- DOTS (directly observed treatment, short course) anti TB therapy
- Contact tracing: the identification and diagnosis of persons who may have come into contact with an infected person
What is your advice to contacts?
-Counselling, screening and treatment of other family members
What is a granuloma?
Organised collection of macrophages fusing to form langerhans giant cells
What are other causes of granuloma?
Infections
-Bacterial (TB, leprosy, syphilis, aspiration pneumonia)
-Parasitic infection (schistosomiasis_
-Fungal infections (Histoplasmosis)
Non infective causes
-Sarcoidosis
-Crohn’s disease
-Rheumatoid arthritis
-Foreign body
What is the pathogenesis of TB?
- Infection begins when mycobacteria reach the alveolar air sacs
- Here they replicate within endosomes alveolar macrophages
- Macrophage attempts to kill mycobacterium but cannot be killed by them due mycolic acid capsule: phagolysosome is ineffective
- Primary infection site in the lung is the Ghon focus: can spread to distant sites from here haematogenously
- Inflammatory cells (macrophages, epitheloid cells, T cells, b lymphocytes, fibroblasts) aggregate to form granulomas with caseous necrosis centrally
- Multinucleate giant cells formed by macrophages
What is a mycobacterium?
-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
Where can TB affect in the body?
-Almost anywhere
-90% of cases in the lungs
-20% outside lungs to pleura/cns/lymphatics/GU system, etc
-What is potts disease, in relation to TB?
-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
What is miliary TB?
-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
How is TB diagnosed?
Active TB:
-1. Fluid samples (sputum/bronchial-alveolar lavage) for acid fast bacilli using auramine-rhodamine or ziehl-nielsen staining
- PCR to differentiate m tuberculosis from other mycobacteria and allow testing for multi drug resistance
- CXR and CT chest (and other imaging modalities if looking for extra-pumonary TB)
Tests for latent TB:
- Interferon gamma release assay e.g. quantiferon blood test. More reliable than mantoux
- 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
How is pulmonary TB treated?
-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
What is a granuloma?
-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
