Patho Slide #8 - TB
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Transcript of Patho Slide #8 - TB
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TUBERCULOSIS
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TuberculosisAncient Disease - New Threat
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TB is an ancient infectious disease
caused byMycobacterium tuberculosis.
It has been known since 1000 B.C.
1900s Approximately all of Europesadult population infected with TB
No treatment
Up till the 50s Sanatorium withEmphasis on rest, good nutrition, andfresh mountainous air
Isolation led to q in transmission
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Meeting held in London (1977)
It was concluded that by 1990Tuberculosis would be rare and by2010 it will only be of historical
interest to the medical fraternity!
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TUBERCULOSIS
Infects one third of world population..!
3 million deaths due to TB every year
Under privileged population
Since 1985 incidence is increasing inwest
AIDS, Diabetes, Immunosuppressedpatients.
Drug resistance
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Communicable disease caused usually by
M. hominis ,bovis, avium,etc.
May affect any organ lung is most affected . Route of infection : Inhalation p Lung
OR Ingestion p Intestine
Not all exposed get infected Genetic makeup linked to NRAMP1
polymorphism
Mostly self limited ,s
viable organisms
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Since TB is a disease of respiratorytransmission, optimal conditions fortransmission include:
overcrowding
poor personal hygiene
poor public hygiene
Poor nutrition
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Transmission
Pulmonary tuberculosis is a disease ofrespiratory transmission, Patients with
the active disease (bacilli) expel theminto the air by:
coughing,
sneezing, or any other way that will expel
bacilli into the air
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Environmental Factors Increase
Risk for Transmission
Exposure in small, enclosed spaces
Inadequate ventilation
Re-circulated air containing infectiousdroplets
I
nadequate cleaning and disinfection ofequipment
Improper specimen-handlingprocedures
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Pathogenesis :
TB bacilli taken up by alveolar macrophages
through action of receptors on their surface Bacilli inhibit microbial killing by interfering
with phagolysosomal function
Proliferation of bacilli inside alveolarmacrophages, then releasedbacteremia
Majority are symptomless
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Inside LN, cell mediated immunity after 3w
CD4+TH
1 subsetIF
N activatemacrophages mediators bacterial
killing
Immune response leads to caseation
Caseation is tissue necrosis, later healing
Outcome of the disease depends on thebalance of immunity to tissue destruction
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Signs and symptoms
Early symptoms
Common cold symptoms
Listlessness, fatigue, fever, a minimallyproductive cough of yellow or greensputum and a general feeling of malaise.
Later symptoms Night sweats, fever, cough with purulent
secretions and haemoptysis, dyspnoea,chest pain, and hoarseness appear.
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Types of TB infection :
1. Primary TB :Infection in unsensitized
or immunocompromised host2. Secondary ( reactivation TB)
3. Progressive pulmonary TB
4. Miliary TB
5. Isolated organ TB
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1- Primary TB :
Subpleural caseating granuloma p
Ghon focusCaseation , surrounded by chronic
inflammatory cells, epitheloid cells &Langhans giant cells
Enlarged hilar LNs with caseation pGhon Complex
Ghon focus + nodal involvement
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GHON COMPLEX
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Caseating granulomata
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Caseating granulomata
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WHAT HAPPENS LATER ???
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Outcome of Primary TB :
- In 95% cell mediated immunity p
healing in 3 weeks
- Fibrosiss calcificationRanke complex
- Uncommonly disseminated disease
Progressive Primary TB
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2. Secondary (Reinfection TB)
Arises in a previously sensitized host inone of following :
Progressive post primary ( < 5% ) Reactivation of old focus
Reinfection with a virulent strain
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Infection is characterized by :
Location usually at apex about 2 cm.size CAVITATION is common Lymph node enlargement less prominent Sputum is positive for TB bacilli in most
cases
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Symptoms :
Hemoptysis common, fever , loss of
weight night sweats, pleuritic pain. Extrapulmonary manifestations if present
May be asymptomatic !
Outcome :
May heal or become progressive
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3. Progressive Pulmonary TBThis can occur after primary or secondaryTB , along the following routes :
Tracheobronchial tree & lymphatics Tuberculous bronchopneumonia OR
Miliary pulmonary disease.
Pleural involvement leads to effusion,empyema or obliterative fibrous pleuritis
Spread through trachea to larynxleads to Laryngeal TB
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Swallowing infected sputum leads to
intestinal TB
Spread through pulmonary veins pHeartp systemic circulation pgeneralized spread
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4. Systemic Miliary TB Numerous tiny tubercles in any organ
Most affected :
Liver
Bone marrow
Spleen
Adrenals
Meninges
Kidneys.etc
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Systemic Miliary TB
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5. Isolated Organ TB Spread through blood p low grade
bacteremia leads to granulomatous
infection in any organ Symptoms depend on the organ:
Tuberculous salpingitis & endometritis
lead to sterility
Vertebral TB p POTTs Disease
Adrenal gland p Addisons disease
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Tuberculous lymphadenitis Scrofuloderma
Renal infection p Tuberculous chronic
Pyelonephritis, nephrotic syndrome
Male Genital system p Tuberculous
epididymo-orchitis & prostatitisp
sterility
Chronic TB p SECONDARY AMYLOIDOSIS
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Adrenal TB - Addison Disease
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Spinal TB - Potts Disease
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Tuberculosis in HIV : Bacterial pneumonias in general are
commoner & more serious than in
immunocompetent patients Tuberculosis in initial phases of HIV is
usually secondary reactivation TB
In late stages : Miliary TB & Atypical TB M.avium common in late stages p
poorly formed granuloma without caseation
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Diagnosis of TB
Clinical picture
X ray picture
Sputum :
Direct examination for Acid FastBacilli
(ZN, Auramine-rhodamine stains, PCR) Culture of sputum about 6 weeks
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Chest X-ray in primary TB
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Later :
Chest x-rays: Multi nodular infiltrateabove or behind the clavicle with or
without pleural effusion unilaterally orbilaterally.
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Diagnosis (continued)
Sputum investigation: Cultures will reveal the presence of
mycobacterium tuberculosis
Patients stay infectious for as long asthe bacilli are excreted in the sputum
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AFB - Ziehl-Nielson stain
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Diagnosis (continued)
Skin test : Tuberculin test
Injecting PPD into skin p
positive ( 48- 72hrs.)
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PPD Testing
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PPD Testing
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Problems of interpretation of test :
It indicates hypersensitivity to bacilli butdoes not differentiate infection from active
disease
False negative in Miliary TB , AIDS,sarcoidosis some viral diseases , Hodgkins
disease , malnutrition False positive in atypical mycobacterial
infection