pedia pulmo 3
DESCRIPTION
pulmo pediatricsTRANSCRIPT
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Pulmonary tuberculosis primary infection
progressive primary infection
Chronic pulmonary TB
multidrug resistant pulmonary tuberculosis
miliary tuberculosis
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TB: Airborne infection
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TRANSMISSION
person to person, generally from adult to child and not vice-versa nor from child to child
Transmission rarely occurs by direct contact with an infected discharge or a contaminated fomite
The lung is the portal of entry in >98% of cases.
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Factors that would ENHANCE transmission
1. when the patient has a positive acid-fast smear of sputum
2. an extensive upper lobe infiltrate or cavity
3. copious production of thin sputum
4. severe and forceful cough
5. Environmental factors such as poor air circulation
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Stages of Tuberculosis
1. Primary infection
2. Progressive primary TB
3. chronic pulmonary TB
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Primary Infection
First infection with tubercle bacilli
Found in children
Clinical course depends on the childs health status
If malnourished widespread (post primary or progressive primary stage)
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Pathogenesis
Inhaled Tb bacilli reaches alveoli nonspecific inflammatory reaction Ghons tubercle or primary focus(initial tissue infection)
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GHONS COMPLEX (Primary complex)
1.Ghons focus subpleural focus in the upper part of lower lobe/ lower part of upper lobe
2. lymphangitis
3. regional (hilar) lymphadenopathy
Develops within 2-8 weeks from onset of infection
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PRIMARY INFECTION
Insiduous onset
Incubation period: 2-10 wks
No symptoms as a rule
But if (+) : Easy fatigability, low grade fever
NOT contagious
Cell mediated immunity is responsible
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Primary Pulmonary TB
BUT if the immune system is weak , there can be disseminated TB
In 3-6 months , it can reach the brain (meningitis, tuberculoma, TB abscess)
In 1 year: bones
In 5-25 yrs : kidneys
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Only Adults Transmit TB
Number of bacilli in sputum
Adult Child
108 104
Need about 105 organisms/ml for positive smear
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Key features suggestive of TB
The presence of three or more of the following should strongly suggest a diagnosis of TB:
Chronic symptoms suggestive of TB
Physical signs highly of suggestive of TB
A positive tuberculin skin test
Chest X-ray suggestive of TB
History of contact with a source
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RISK for DISSEMINATION
Conditions that adversely affect cell-mediated immunity predispose to progression from tuberculosis infection to disease (HIV, AIDS)
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BCG VACCINE
Used as a diagnostic test for TB
If the child is previously sensitized to tuberculo protein accelerated local response
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BCG VACCINE
Dose: 0.05ml for NB up to 1 month
0.1ml for >1month
Route: intradermal
Within 2-3 weeks induration
4-6 weeks pustule
Healing in 8-12 weeks time
Efficacy: >50-80%
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BCG VACCINE
Cannot prevent people from getting primary TB
BUT it can prevent people from getting extrapulmonary TB ( meningitis, diseminated TB, etc)
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Tuberculin Skin Test (Mantoux test)
Intradermal injection of 0.1ml of PPD
amount of induration is measured in 72 hr
Once positive, a PPD will always be positive.
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Mantoux test
Sensitized lymphocytes (CD4 and CD8) recognize the antigen local inflammation
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False positive results
Prevalence of non-tuberculous mycobacteria
Prior BCG vaccination
Repeated TST resulting in sensitization
Incorrect interpretation of the result
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False negative results
Severe tuberculosis
Previous viral disease
Very young age (
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Interpretation of TST size of induration interpretation
(regardless of BCG status)
>15 mm strongly POSITIVE
> 10mm POSITIVE
> 5mm Positive if any of the ff is present: immunocompromised state, history of
contact with source-case, signs and symptoms suggestive of TB, CXR
findings suggestive of TB
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LAB
Sputum exam
traditional culture specimen in young children is the early morning gastric acid obtained before the child has arisen and peristalsis has emptied the stomach of the pooled secretions that have been swallowed overnight.
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Interferon Gamma Release Assay (IGRA)
Involves measurement of interferon-gamma (IFN-) released by T cells that have been sensitized by a prior exposure to M. tuberculosis
Response is measured after 1-24 hrs of incubation using ELISA or enzyme-linked immunospot (ELISPOT)
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Interferon Gamma Release Assay (IGRA)
Expensive
Excellent specificity and good sensitivity
Do not distinguish LTBI from active TB disease
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Nucleic acid amplification methods (NAATs)
Uses polymerase chain reaction
Positive NAATs support the diagnosis of TB but a negative result does not rule it out
Hence, they are not a replacement for conventional lab methods like AFB smear and culture
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How is TB cured?
TB can be cured. DOTS (Directly-Observed Treatment Short
Course) is the recommended strategy to cure TB.
It ensures the right combination and dosage of anti-TB drugs.
It ensures regular and complete intake of anti-TB drugs.
Patient takes drugs every day with the help of a treatment partner.
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CHEMOPROPHYLAXIS
Primary chemoprophylaxis
Given to tuberculin negative neonates, infants and children
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TREATMENT
6 month regimen of Isoniazid (H), rifampicin (R) and 2 months of pyrazinamide (Z)
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Ethambutol used in children with life- threatening TB or who are at risk for drug resistant tuberculosis
Streptomycin used to replace Ethambutol for children below 6 yrs and in the treatment of TB meningitis; reserved for multi-drug resistant TB
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2 Phases of treatment: The intensive phase usually covers the first 2 months of
treatment. During this phase, most of the bacilli will be
killed. The sputum converts from positive to
negative in more than 80 % of the new patients within the first 2 months of treatment.
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Phases of treatment: The continuation phase usually lasts 4-6 months, depending on the
treatment regimen. intended to eliminate the remaining dormant
bacilli. Since it is not possible to identify which
patients still have dormant bacilli, all patients should continue their treatment until the end of the prescribed period, to limit the number of relapses.
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Common side effects:
Ethambutol : optic neuritis
INH : peripheral neuropathy
Rifampicin : Hepatotoxicity
Streptomycin: ototoxicity and vestibular dysfunction
Pyrazinamide - hepatotoxicity
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Evaluation of response to TB
(-) Anorexia 3-6 months
(-) pulmonary infiltrates 2-9 months
(-) Hilar adenopathy 2-3 years
(-) Pleural effusion 6-12 wks
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2. Progressive Primary Pulmonary Disease
A rare but serious complication of TB in a child occurs when the primary focus enlarges steadily and develops a large caseous center.
Liquefaction can cause formation of a primary cavity associated with large numbers of tubercle bacilli.
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2. Progressive Primary Pulmonary Disease
s/s: child looks ill; distressing cough
sputum positive
Dx: CXR bronchopneumonic foci
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3. Chronic Pulmonary TB
Aka Reactivation TB, Phthisis
usually represents endogenous reactivation of a site of tuberculosis infection established previously in the body.
Occurs in older children >10 years of age
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Children with a healed tuberculosis infection acquired at 7 yr of age.
Usually happens in malnourished children
3. Chronic Pulmonary TB
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3. Chronic Pulmonary TB
Now with the apical seedings (Simon foci) established during the hematogenous phase of the early infection.
usually remains localized to the lungs, because the established immune response prevents further extrapulmonary spread.
CXR: infiltrates or thick-walled cavities in the apex of the upper lobes, where oxygen tension is high and poor lymphatic drainage
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Miliary Tuberculosis
A serious post primary complication due to massive invasion of the blood stream by tubercle bacilli
result in dissemination of the bacilli and a miliary pattern, with small nodules evenly distributed on the chest radiograph
Involves 2 or more non-contiguous anatomic sites (disseminated)
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Miliary Tuberculosis
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3 clinical forms of Miliary TB
1. typhoidal
2. pulmonary
3. meningeal
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Extrapulmonary Tuberculosis
Disease involving anatomic structures other than the lung parenchyma
Most common form Tuberculous lymphadenitis (scrofula)
Results from lymphohematogenous spread
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Drug - resistant TB
is a laboratory diagnosis
Features of a child suspected of having drug-resistant TB:
contact with a known case of drug-resistant TB
not responding to the anti-TB treatment regimen
recurrence of TB after adherence to treatment
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All mono-therapeutic regimens (real or masked by combination with drugs to which bacilli are resistant) lead to treatment failure and to the development of resistance.
When three or more drugs are administered, the risk of resistance is practically zero.
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spectrum of childhood TB
TB exposure: child with close contact a source case, no s/sx, (-) TST, no radiologic or lab findings for TB
TB infection: child with (+) TST, no radiologic or lab findings for TB
TB disease: child is TB symptomatic, (+) TST and/or positive radiologic or lab findings suggestive of TB
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TUBERCULOSIS Clinical manifestations in pediatric TB may be
non-specific
TB is much more difficult to diagnose in children
Undiagnosed or untreated TB in a child is potentially serious,
More likely to develop severe or disseminated disease
Knowing how to administer and read PPDs, and to contextually interpret PPDs and CXRs is vital