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Pathophysiology of
Tuberculosis
Pratik Godhani
Pharmacy Management.
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Introduction
Tuberculosis (TB) is a communicable infectious disease caused
by Mycobacterium tuberculosis. It can produce latent
infection as well as progressive, active disease.
M. tuberculosis is transmitted from person to person bycoughing or sneezing or close contacts of TB patients.
WHO
13 million chronic active cases + 9.3 million new cases
(3.4 million cases in India only)
T.B. occurs at rate of one per second.
Market of Anti tuberculosis drugs and vaccines by 2011 is
expected to reach 670 million USD.
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Mycobacterium tuberculosis is spread by small airborne
droplets, called droplet nuclei, generated by the coughing,
sneezing, talking, or singing of a person with pulmonary or
laryngeal tuberculosis.
Introduction ofM tuberculosis into the lungs leads to infection
of the respiratory system.
However, the organisms can spread to other organs, such as
the lymphatics, pleura, bones/joints, or meninges, and cause
extrapulmonary tuberculosis.
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PATHOPHYSIOLOGY
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Droplet nuclei with
bacilli are inhaled, enter
the lung, and deposit in
alveoli.
Macrophages and T
lymphocytes act together
to try to contain the
infection by forming
granulomas.
In weaker immune systems, the
wall loses integrity and the
bacilli are able to escape and
spread to other alveoli or other
organs.
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CLINICALPRESENTATION
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Early infection :
Immune system fights infection.
Infection generally proceeds withoutsigns or symptoms.
Patients may have fever, paratracheallymphadenopathy, or dyspnea. Infectionmay be only subclinical and may notadvance to active disease.
Early primary progressive :
Immune system does not control initialinfection.
Patients often have nonspecific signs orsymptoms (eg, fatigue, weight loss,fever).
Nonproductive cough develops.Diagnosis can be difficult: findings onchest radiographs may be normal and
sputum smears may be negative formycobacteria.
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Late primary progressive:
Cough becomes productive.
More signs and symptoms asdisease progresses. Patients
experience progressive weight loss,rales, hemoptysis.
Findings on chest radio -graph arenormal, may show cavity.Diagnosis:cultures of sputum.
Latent:
Mycobacteria persist in the body.Nosigns or symptoms occur.
Patients do not feel sick. Patients aresusceptible to reactivation ofdisease.
Infection can reappear whenimmunosuppression occurs.
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DIAGNOSIS
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TEST NAME DESCRIPTION
RADIOGRAPHY Patchy or nodular infiltrates and Cavitation in the apical
areas of the upper lobes or the superior segment of the
lower lobes.
SPUTUM CULTURE IDENTIFY M.Tuberculosis (4-7 days with HPLC)POLIMERASE CHAIN
REACTION
Identify M. tuberculosis, (1-2 hrs)
TUBERCULIN SKIN TEST
QUANTIFERON- TB TEST Measure immune reactivity to M.tuberculosis (12-14 hrs)
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Chest radiograph shows
presence ofCavitation in
affected part of Lung
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TUBERCULIN SKIN TEST
Infection with M. tuberculosis produces a delayed
hypersensitivity skin reaction to certain components
of bacterium(purified protein derivatives PPD)
Administer 0.1 ml volume containing 5 TU of PPD
into top layers of skin of the forearm
Reading after 48-72 hours of injection.
Observe presence or absence of induration (localizedswelling).
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Positive Tuberculin Skin Test:
Diameter (mm) Considered positive for
5
Persons at high risk for tuberculosis:
Patients with chronic diseases (e.g., infection with human
immunodeficiency virus)Persons with recent exposure to tuberculosis
Employees of hospitals and long-term care facilities
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Persons at risk for tuberculosis:
Injectable drug users, Persons in close living conditions
Persons born in countries with high prevalence of
Tuberculosis,Persons with following clinical conditions : silicosis;
diabetes mellitus; chronic renal failure; some hematologic
disorders (e.g., leukemias and lymphomas);
15 Persons with no risk factors for TB
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THANKYOU