Ptb Flashcards
- recognized subset of T helper cells
- importante modulator of inflammation and CD4+ T cell recall or memory response.
- secretes IL17
- can recruit neutrophils, monocytes and CD4+ T cells producing IFN y and stimulate chemokine expression
Th17 cells
- indicated by the negatives tuberculin test —
ANERGY
Causes of anergy or negatives tuberculin test:
- malnutrition
- HIV infection
- steroid therapy
- severe TB (due to productions of inhibitory cytokines like TGF-B)
- kill cells garbo rin intracellular pathogens,
- either exhibit granzyme/perforin-mediated killing of target T cells (first step: cell membrane destroyed) or induce apoptosis (destruction of target T-cell DNA —> LYSIS)
CYTOLYTIC or CYTOTOXIC T-LYPMPHOCYTES
- like CD8 T cell
- assoc. with inc. Replication of mycobacterial rather that susceptibility to TB
- Foundation in chromosomes 2
- linked with BCG resistance gene
Nramp (natural resistance assoc. Macrophage protektahan)
TB responsed and course
TB bacilli -> alveoli -> alveolar macrophages
Can evade intracellular killing mechanism -> Get carried to lymph Nodes and other organs.
In lungs macrophages introduce antigens to T cells -> resulting in its expansion, Development of memory Tcell of which DTH cells may be a subset -> may result tuberculin positive persistence and/or long term Protection.
Inflammatory Th1 responses -> local pulmonary infiltrates and hilar Adenopathy (PRIMARY COMPLEX).
If unable to contain: cause progressive dse -> imbalance between proinflammatory and immunosuppressive effects -> military TB
Development of progression TB occurs in ___ % of affected individuals?
10%
- After adequate treatment, some bacilli persist in a dormant state.
- clinically asymptomatic
- reactivation of dormant bacilli lead to active disease
Patent TB infection
LTBD
Factors that prompte Development and Ma Inten ace of latency?
- Low concert ratio of O2
- Nutrients in chronic granulomas
- Local production of TNF - alpha and Nitric oxide
Maintaned in Latent phase:
- TNF - alpha
- IFN - Gamma
- NO
Reactivation of TB occurs at extrapulmonary site without apparently lung lessons in ___ % of affected individuals?
15%
Leads to reactivation due to depression of cell mediated immunity:
- HIV infection
- malnutrition
- disease
- Druidrider
What age is particularly susceptible to Develop TB and are at increased risk of developing disseminated dse, particularly TBM.
Under 2yrs of age
Reason: weaker innate and adaptive responses / immaturity of immune system
Congenital infection identified possible reasons for the Development of dse:
- Impaired antigen-specific CD4p T-lymphocyte responses
- Decreased capacity of Neonatal T-lymphocytes to Secrets IFN-Y, and TNF-alpha
- cytokine production leans towards a Th2 response
- Suboptimal response of CD8p T-lymphocyte.
TB source:
- exposure
- environmental factors: overcrowding, poot Ventilation
Risk factors for TB:
AEI
- Household contact with a newly diagnosed Smear + case
- depends on the infectivity, proximity and duration of contact
- Age less than 5years
- most important factor
- determined the risk of progression to disease following primary infxn
Among immunocompetent children. - infants are at greatest risk
- risk remains significant in the 2nd yr if life
- lowest in children 5-10yo.
- Immunocompromised state (severe mal., HIV)
- host immunity, major determinant of dse develop´n
- high risk
Infectivity of smear positive vs smear negative household exposure?
60 to 80%
30 to 40%
TB morbidity with Family history exposure
2.5 Times than without knowing exposure
Additional groups at high risk of exposure and infection?
- residents and employees of closed settings
- medically underserved, low income populations
- high-risk racia and ethinic minority populations
- infection drug users
- children exposed to adults with certain medical conditions.
TB transmission and portal of entry:
- airborne
- inhalation of dropped nuclei
- 5micra
- 5 to 200 inhaled bacilli
Perinatal transmission of TB occur:
- transplacentally through umbilical vein from mother with primary hematogenous TB daring pregnancy
- aspiration/ingestion of infected AF in utero/daring delivery
- inhalation of TB bacilli at or soon after delivery (most common)
TB incubation period:
3 to 12 weeks
Shorter when the inoculum is large
Primary infection
- Occurs in person without previous exposure to tubercle bacilli.
- controlled with a reactive tuberculin skin test as the only evidence of infection.
Pathogenesis
Inhalation —> scavenging noon-activated, alveolar macrophages ingest the tubercle bacilli —> if not inhibited (virulance, microbicidal ability of macrophages) —> unrestrained replication —> some macrophages carry bacilli from lung to regional (hilar and mediastinal) lymph nodes —> disseminated via lymphatics or bloodstream (kidney, meninges, epiphyseal plates of long bones, vertebrae, apical segments of the upper lobes lungs) —> infected macrophages present tuberculous antigens to T lymph —> T-lym sensitized —> produce progeny —> secrete lymphokines (IFN-y, TNF) and activates macrophages —> inc lyrics enzyme (epitheloid macrophages, langhans giant cells)
CMI and DTH both inhibit the inc in Number of bacilli
The response of activated T-lymph in response to M. Tuberculosis antigen
Delayed-type hypersensitivity (DHT)
Comprises the increased capacity to ingest and destroy the bacilli of activated macrophages
Cell-mediated immunity
- Classic lesson in the lung of primary tuberculosis
- a caseous granuloma
- located peripherally in any part of lungs, close to pleura
GHON FOCUS
Soft, semi solid core surrounded by epithelioid macrophages, langhans giant T-cells and lymphocytes
Granuloma
Dissemination of bacilli from the primary granuloma in the lungs to the hilar nodes causes?
Granulomatous lymphadenitis
Combination of granulomatous hilar lymphadenitis and ghons focus
GHON COMPLEX
If immune mechanisms wane or fail
Lesions of the ghon complex (both lungs and lymph nodes) —>
Heal by FIBROSIS —> CALCIFICATION —>
Some die, few remain viable —>
REACTIVATE LATER (if immune mechanisms wane or fail)
- freq. result in disseminated dse.
- occurs when immune system is weakened and fails
- may be brought about by state of immunosuppression
- observed more commonly under 2yo.
Progressive primary tuberculosis
Pathogenesis of progressive primary TB —> Middle lobe syndrome
Primary Focus enlarges —> large caseous Center —>
Liquefies to form a primary cavity —> allowing TB bacilli to multiply extensively —> erosion of infected debris into bronchus —>
Causing futher intrapulmonary spread
Enlarging hilar and mediastinal nodes —> compress the bronchi —>
Cause collapse of distal lung (MIDDLE LOBE SYNDROME)
If obstruction is partial —> cause air-trapping and overdistension of a lobe or segment.
Pathogenesis of progressive primary TB —> Disseminated TB (miliary dse)
Occult lymphohematogenous spread —> Development of hypersensitivity to tuberculous antigens
- analogous to bacterial sepsis
- progressive caseous necrosis (usually hilar lymph nose) —> erodes into a blood vessel (pulmonary vein) —> bacilli spread (lungs, liver, spleen, bone marrow, meninges)
- consist of numerous small, yellow-white nodules, <2mm (millet seed-like) in all affected organs.
- denote all forms of progressive, widely disseminated hematogenous TB, even if the classical pathologic or radiologic findings are absent.
Disseminated TB (miliary TB)
- Occurs following re-infection with M.TB or reactivation of dormant bacilli in the ghon focus or complex.
- tissue destruction is brought about by progressive, freq. extensive caseous necrosis due to inability to contain bacteria.
- the course is variable
- localized inflammation —> may undergo organization and healing into a fibrocalcified nodule —> progress into caseating granulomas with cavitation or disseminate to other organs via rupture into a bronchus, pulmonary artery, pulmonary vein or lymphatics.
Secondary (adult-type) TB
Pathogenesis of secondary (adult-type) TB
- localized inflammation —> may undergo organization and healing into a fibrocalcified nodule —> progress into caseating granulomas with cavitation or disseminate to other organs via rupture into a bronchus, pulmonary artery, pulmonary vein or lymphatics.
Described the early course and progression over time of TB
Wallgren’s timetable of TB
3 to 13 wks - (after primary infxn)
1 to 3mon - (after primary infxn)
3 to 7 mons - (after primary infection)
1 to 3yrs - (after primary infection)
> 3yrs - (after primary infxn)
1st 5yrs - (after initial infxn)
5 to 25yrs - (after initial infxn)
3 to 13 wks - (after primary infxn) end of initial asymtomatic
incubation period.
- characterized by hypersensitivity rxns (fever, erythema
nodosum, +TST response, primary complex on CXR)
- hypersensitivity to tuberculoprotein antigens once
developed after infxn is expected to remain reactive for life.
1 to 3mon - (after primary infxn) following occult hematogenous spread
during incubation, highest risk for TB MENINGITIS &
DISSEMINATED & MILIARY TB.
- TB meningitis & miliary TB may also occur after anytime
interval.
3 to 7 mons - (after primary infection)
<5yo: period of secondary airway involvement due to infected
lymph nodes.
>5yo: large reactive pleural effusions can also occur.
1 to 3yrs - (after primary infection)
<5yo: period of osteoarticular TB
Adolescent: adult-type dse. May have delayed clinical onset after
calcification, ranging from as early 3mon to as late as 20yrs.
- risk for TB progression following primary infection is much less by
the time calcification appears.
> 3yrs - (after primary infxn) when calcification is completed.
- highest risk period have passed.
- very late manifestations of TB my occur (primary pulmonary
reactivation)
1st 5yrs - (after initial infxn) complications of TB occur.
- Arrested or silent lesion may reactivate, heralding complications.
5 to 25yrs - (after initial infxn) renal involvement appears.
Risk to develop TB of Immunocompetent adult w/o tx?
5-10% risk to develop TB during the lifetime
Risk in immunicompetent infants with untreated TB infxn?
Serious life threatening forms of the disease will develop within 1 to 2 years in a many as 40%
3 to 13 wks - (after primary infxn) end of ?
- characterized by?
- hypersensitivity to tuberculoprotein antigens once
developed after infxn is expected to?
3 to 13 wks - (after primary infxn) end of initial asymtomatic
incubation period.
- characterized by hypersensitivity rxns (fever, erythema
nodosum, +TST response, primary complex on CXR)
- hypersensitivity to tuberculoprotein antigens once
developed after infxn is expected to remain reactive for life.
1 to 3mon - (after primary infxn) following occult hematogenous
spread during incubation, highest risk for?
- may also occur after anytime interval.
1 to 3mon - (after primary infxn) following occult hematogenous
spread during incubation, highest risk for TB MENINGITIS &
DISSEMINATED & MILIARY TB.
- TB meningitis & miliary TB may also occur after anytime
interval.
3 to 7 mons - (after primary infection)
<5yo: period of?
>5yo: what occurs?
3 to 7 mons - (after primary infection)
<5yo: period of 2dary airway involvement due to infected
lymph nodes.
>5yo: large reactive pleural effusions can also occur.
1 to 3yrs - (after primary infection)
<5yo: period of?
Adolescent: adult-type dse. May have delayed clinical onset after?
ranging from?
- risk for TB progression following primary infection by the time
calcification appears?
1 to 3yrs - (after primary infection)
<5yo: period of osteoarticular TB
Adolescent: adult-type dse. May have delayed clinical onset after
calcification, ranging from as early 3mon to as late as 20yrs.
- risk for TB progression following primary infection is much less by
the time calcification appears.
> 3yrs - (after primary infxn) when calcification is completed.
- highest risk period have? - very late manifestations of TB?
> 3yrs - (after primary infxn) when calcification is completed.
- highest risk period have passed.
- very late manifestations of TB may occur (primary pulmonary
reactivation)
1st 5yrs - (after initial infxn) what occurs?
- what may reactivate, heralding complications?
1st 5yrs - (after initial infxn) complications of TB occur.
- Arrested or silent lesion may reactivate, heralding.
complications.
5 to 25yrs - (after initial infxn) involvement appears on?
5 to 25yrs - (after initial infxn) renal involvement appears.
TB-related mortality:
- infants
- under 3mon age
- highest risk following primary infection at 5-10%
- more likely to develop more severe forms of TB
- 13% of children under 3mon with TB died.
TB-related mortality:
- between 1 to 4yo?
- risk decreases to 1%
TB-related mortality:
- 5 to 14yo?
- below 10yrs old
- lowest risk at <0.5%
- majority of deaths occurred within the 1st yr following the primary infection
TB-related mortality:
- after 15 yo
- older children who developed adults-type cavitary dse,
- risk inc. to >2%
- older children who developed adults-type cavitary dse, mortality declined more slowly
TB-related mortality:
- from sputum smear + household source case
- among TST + reactors
- mortality is almost twice as high compared to a infxn from an unknown source case.
- mortality rate is 3x inc among TST + reactors than those who are TST - reactors
How mycobacterium tuberculosis produce infection and dse in almost every tissue and organ in the body?
- result of dissemination from an initial primary focus.
- infxn usually takes place by way of the respiratory tract, the lung is the first organ involved and it is here that the initial major manifestations of dse occur,
Distinction between TB infxn and dse?
- Primary infxn: patients are asymptomatic
- Disease is present: early manifestations are mild with nonspecific systemic symptoms of:
low-grade fever,
lassitude,
easy fatigability,
anorexia,
weight loss or faltering,
malaise,
night sweats - progression and chronicity, symptoms maybe respiratory or other manifestations, depending on the main site.
A condition in which a child is in:
- close contact with contagious adult or adolescent TB cases,
- no signs and symptoms of TB
- negative TST reaction
- no radiologic
- no laboratory findings suggestive of TB
TB exposure
Negative for everything
A condition in which a child has:
- no signs and symptoms presumptive of TB
- no radiologic
- no laboratory evidence
- positive TST reaction
TB infection or Latent TB infection (LTBI)
A presumptive TB who after clinical and diagnostic evaluation (TST and/or radiology) is confirmed to have TB.
TB disease
TB disease Classification:
- Bacteriological status ~ Bacteriological - confirmed ~ Clinically - diagnosed - Anatomical site ~ Pulmonary TB (PTB) ~ Extrapulmonary TB (EPTB)
Bacteriological status where biological specimen is positive by:
- smear microscopy,
- culture or rapid diagnostic tests (such as Xpert MTB/RIF)
Bacteriologically -confirmed TB Disease
Bacteriological status
- that does not fulfil the criteria for bacteriological confirmation but has been diagnosed with active TB by a clinical or other medical practitioner who had decided to give the patient top full course of TB treatment.
- cases diagnosed on the bases of x-ray abnormalities or suggestive histology and extrapulmonary cases w/o laboratory confirmation are also included.
Clinically - diagnosed TB disease
- TB disease based on anatomical site
- Refers to a case of TB involving the lung parenchyma and tracheobronchial tree.
- a patient with both pulmonary and extrapulmonary TB
Pulmonary TB (PTB)
- TB disease based on anatomical site
- refers to a case of TB involving organs other than the lungs and tracheobronchial tree (eg. Larynx, pleura, lymph nodes, abdomen, genitourinary tract, skin, joints and bones, meninges).
Extrapulmonary TB (EPTB)
A patient with both pulmonary and extrapulmonary TB should be classified as a case of?
Pulmonary TB
Histologically Diagnosed EPTB through biopsy of appropriate sites will be considered?
Clinically diagnosed TB
Laryngeal TB, likely through sputum smear positive result, is considered an?
Extrapulmonary TB in the absence of lung infiltrates on CXR.
Pulmonary TB in presence of lung infiltrates on CXR.
The initial stage in children who inhale the mycobacterium tuberculosis bacilli?
Primary Disease
- 3 elements of primary disease
- in 95% of cases, it heals by fibrosis and/or calcification
- Ghon focus
- Lymphadenitis
- Lymphangitis
- asymptomatic in up to 65%
- no striking clinical manifestations
- signs and symptoms can vary substantially in the population although infants and young children are likely to have more signs and symptoms than school-aged children.
Primary TB in children