patho slide #8 - tb

8/7/2019 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

patho slide #8 - tb

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