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Tb path & pathogenesis

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Tb path & pathogenesis

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Tb path & pathogenesis

  1. 1. Dr. Aswini Kumar MohapatraDr. Aswini Kumar Mohapatra Professor and HeadProfessor and Head Dept. of Pulmonary MedicineDept. of Pulmonary Medicine
  2. 2. TUBERCULOSISTUBERCULOSIS PATHOLOGYPATHOLOGY && PATHOGENESISPATHOGENESIS
  3. 3. PATHOLOGY & PATHOGENESISPATHOLOGY & PATHOGENESIS Lung- predominant primary siteLung- predominant primary site  Mycobacterium tuberculosisMycobacterium tuberculosis  Mycobacterium bovisMycobacterium bovis (rare occurrence(rare occurrence because of pasteurization of milk)because of pasteurization of milk)  NTMNTM -- Non Tuberculous Mycobacteria-Non Tuberculous Mycobacteria- immunodeficient populationimmunodeficient population
  4. 4. Mycobacterium tuberculosisMycobacterium tuberculosis-- non motilenon motile aerobicaerobic catalase producingcatalase producing acid fast bacillusacid fast bacillus (AFB)(AFB) Tuberculosis is transmitted by aerosolTuberculosis is transmitted by aerosol.. PTB is the predominant form of diseasePTB is the predominant form of disease Extra pulmonary TB is commonlyExtra pulmonary TB is commonly accompanied by pulmonary diseaseaccompanied by pulmonary disease
  5. 5. PATHOLOGYPATHOLOGY PTB -PTB - Primary TBPrimary TB Post- primary TBPost- primary TB Primary TBPrimary TB-- Infection occurring for the first timeInfection occurring for the first time Most characteristic feature-Most characteristic feature- GHON’S COMPLEXGHON’S COMPLEX (PRIMARY COMPLEX)(PRIMARY COMPLEX)
  6. 6. GHON’S COMPLEXGHON’S COMPLEX-- 1. Pulmonary focus1. Pulmonary focus (Ghon’s focus)(Ghon’s focus) a sub pleural focusa sub pleural focus usually < 1cm in dia.usually < 1cm in dia. can occur anywhere in the lungcan occur anywhere in the lung 2. Draining lymphatics2. Draining lymphatics 3. Hilar nodes3. Hilar nodes Lesions present in the primary focus asLesions present in the primary focus as well as lymphnodes -well as lymphnodes - TuberclesTubercles
  7. 7. TUBERCLETUBERCLE-- 1.Epitheloid cells1.Epitheloid cells 2.langhan’s giant cells2.langhan’s giant cells 3.Lymphocytes3.Lymphocytes Centre of the tubercle may undergo necrosis-Centre of the tubercle may undergo necrosis- caseation necrosiscaseation necrosis
  8. 8. Fate of primary complexFate of primary complex-- Most heal with or without calcificationMost heal with or without calcification Bacilli escape from the draining nodes toBacilli escape from the draining nodes to the circulation and then to other parts ofthe circulation and then to other parts of lung and other organslung and other organs May fail to healMay fail to heal →→ progressive primaryprogressive primary TBTB Enlarged lymhnodes may compressEnlarged lymhnodes may compress airwaysairways →→ collapse of lobes / segmentcollapse of lobes / segment EPITUBERCULOSISEPITUBERCULOSIS
  9. 9. Nodes-may erode the airwaysNodes-may erode the airways →→ discharge caseous material into thedischarge caseous material into the airwaysairways →→ acute tuberculousacute tuberculous pneumoniapneumonia Infection from nodes-Infection from nodes- pleura (pleurisy)pleura (pleurisy) pericardium (pericarditis)pericardium (pericarditis) Infection from sub pleural focusInfection from sub pleural focus →→ spreadspread to pleurato pleura →→ pleural effusionpleural effusion
  10. 10. Post primary TBPost primary TB-- Reactivation of latent tuberculosisReactivation of latent tuberculosis Site of lesions-Site of lesions- Posterior segment of upper lobePosterior segment of upper lobe Superior segment of lower lobeSuperior segment of lower lobe
  11. 11. Most characteristic lesionMost characteristic lesion →→ cavitycavity Cavity contains large no. of bacilli (up to 10Cavity contains large no. of bacilli (up to 1099 organisms)organisms) May spread endobronchially to other parts ofMay spread endobronchially to other parts of the lungthe lung Invasion of the vessel on the wall of theInvasion of the vessel on the wall of the cavitycavity →→ haemoptysishaemoptysis
  12. 12. Rupture of the cavity into the pleural spaceRupture of the cavity into the pleural space TB empyemaTB empyema pneumothoraxpneumothorax Prolonged and repeated exposure isProlonged and repeated exposure is essential for a full blown disease processessential for a full blown disease process Smear positive PTBSmear positive PTB →→ “OPEN CASE”“OPEN CASE” →→ readily transmit infectionreadily transmit infection
  13. 13. PATHOGENETIC STAGESPATHOGENETIC STAGES-- 4 stages4 stages Stage-IStage-I stage of onset / stage of nostage of onset / stage of no bacillary growthbacillary growth Stage-IIStage-II stage of symbiosisstage of symbiosis Stage-IIIStage-III stage of immunological controlstage of immunological control Stage-IVStage-IV stage of liquefactionstage of liquefaction
  14. 14. CLINICAL FEATURESCLINICAL FEATURES SymptomsSymptoms-- disease of protean manifestations and mimicdisease of protean manifestations and mimic many diseases.many diseases. Constitutional & Respiratory symptoms.Constitutional & Respiratory symptoms. ConstitutionalConstitutional-- Tiredness, headache, weight loss, fever, nightTiredness, headache, weight loss, fever, night sweats and loss of appetitesweats and loss of appetite  Fever- late afternoon or eveningFever- late afternoon or evening  Associated laryngeal TB- hoarseness ofAssociated laryngeal TB- hoarseness of voicevoice  AmenorrhoeaAmenorrhoea
  15. 15. RespiratoryRespiratory-- CoughCough-- most commonmost common →→ min. 3 weeks duration,min. 3 weeks duration, dry or productivedry or productive Sputum may be mucoid, mucopurulent, purulent orSputum may be mucoid, mucopurulent, purulent or blood tingedblood tinged Haemoptysis-Haemoptysis- blood stain sputum, massive haemoptysis (rupture ofblood stain sputum, massive haemoptysis (rupture of bronchial artery)bronchial artery) Chest pain-Chest pain- dull achingdull aching acute chest pain- TB pleurisyacute chest pain- TB pleurisy pneumothoraxpneumothorax
  16. 16. Breathlessness-Breathlessness- extensive tuberculosisextensive tuberculosis bronchial obstructionbronchial obstruction pneumothoraxpneumothorax pleural effusionpleural effusion Localized wheeze-Localized wheeze- endobronchial TBendobronchial TB ( pressure of enlarged lymph( pressure of enlarged lymph nodes on the bronchus )nodes on the bronchus )
  17. 17. Signs-Signs- Anaemia, cachexiaAnaemia, cachexia Tachycardia- proportionate to feverTachycardia- proportionate to fever Clubbing - advanced cases with superaddedClubbing - advanced cases with superadded suppurationsuppuration Respiratory system examination-Respiratory system examination- Asymmetry of chest wall –retraction, fibrosis orAsymmetry of chest wall –retraction, fibrosis or collapsecollapse Trail’s signTrail’s sign High-pitched bronchial breathing (tubular)High-pitched bronchial breathing (tubular) →→ TBTB pneumoniapneumonia Low pitched bronchial breathing (cavernous)Low pitched bronchial breathing (cavernous) →→ cavity, open pneumothoraxcavity, open pneumothorax
  18. 18. Fine crepitationsFine crepitations →→ post-tussivepost-tussive crepitationcrepitation →→ sign of tuberculosissign of tuberculosis infiltrationinfiltration Post-tussive suctionPost-tussive suction →→ over a cavityover a cavity after coughing when its walls are not tooafter coughing when its walls are not too rigidrigid→→ occurs due to re-entry of airoccurs due to re-entry of air
  19. 19. DIAGNOSISDIAGNOSIS 1.Laboratory1.Laboratory 2.Roentgenography(chest x-ray)2.Roentgenography(chest x-ray) Laboratory-Laboratory- sputumsputum--  Gold standard in the diagnosisGold standard in the diagnosis  Detection of AFB in stained smear to be examinedDetection of AFB in stained smear to be examined microscopicallymicroscopically  3 sputum samples to be examined3 sputum samples to be examined (SPOT-(SPOT- MORNING- SPOT)MORNING- SPOT)  MethodMethod →→ Z-N staining (Ziehl- Neelson carbolZ-N staining (Ziehl- Neelson carbol fuchsin stain)fuchsin stain)  Sample should contain 10,000 AFB/ml for the AFBSample should contain 10,000 AFB/ml for the AFB to be detected by smear examinationto be detected by smear examination
  20. 20. Slide reportingSlide reporting-- No. of bacilli /smearNo. of bacilli /smear resultresult No AFB/100 oil immersion field 0No AFB/100 oil immersion field 0 1-9 AFB/100 oil immersion field scanty1-9 AFB/100 oil immersion field scanty 10-99AFB/100oil immersion field + (1+)10-99AFB/100oil immersion field + (1+) 1-10 AFB/oil immersion field ++ (2+)1-10 AFB/oil immersion field ++ (2+) >10 AFB/oil immersion field +++ (3+)>10 AFB/oil immersion field +++ (3+)
  21. 21. Gastric lavageGastric lavage  diagnosis of PTB in young children instead ofdiagnosis of PTB in young children instead of sputumsputum  lavage reveal organism in 30to40% of the caseslavage reveal organism in 30to40% of the cases  performed early in the morningperformed early in the morning →→ concentration isconcentration is highesthighest  Nasogastric tube- stomach contents are aspiratedNasogastric tube- stomach contents are aspirated Fibreoptic bronchoscopyFibreoptic bronchoscopy Bronchoscopic aspirate, bronchial washing,Bronchoscopic aspirate, bronchial washing, bronchoalveolar lavage(BAL)fluid, Trans bronchialbronchoalveolar lavage(BAL)fluid, Trans bronchial lung biopsylung biopsy UrineUrine CSFCSF TissueTissue biopsy specimens of lymph node, liverbiopsy specimens of lymph node, liver
  22. 22. Culture methodsCulture methods-- Yield from culture is on average twice as that ofYield from culture is on average twice as that of microscopymicroscopy Two types of media commonly usedTwo types of media commonly used 1.egg based1.egg based →→ L-J media, Pentragnani media,L-J media, Pentragnani media, ATS mediaATS media 2.agar based2.agar based →→ Middle brook 7H10,7H11 mediaMiddle brook 7H10,7H11 media Advantage-Advantage- (a) more sensitive and can be positive when the(a) more sensitive and can be positive when the bacterial load in the sample is about 10AFB / mlbacterial load in the sample is about 10AFB / ml (b) for precise identification of the causative(b) for precise identification of the causative organismorganism Disadvantage-Disadvantage- result is delayed, min.6 wks., whereas in smear itresult is delayed, min.6 wks., whereas in smear it is easy to perform and is cheapis easy to perform and is cheap
  23. 23. Chest radiographyChest radiography-- No chest x-ray pattern is absolutely typical of PTBNo chest x-ray pattern is absolutely typical of PTB Classical patternClassical pattern atypical patternatypical pattern (common in HIV)(common in HIV) Upper lobe infiltrate interstitialUpper lobe infiltrate interstitial infiltrates (lower zone)infiltrates (lower zone) B/L infiltratesB/L infiltrates Cavitation no cavitationCavitation no cavitation In vast majority of pts.(>90%)with cavitary PTBIn vast majority of pts.(>90%)with cavitary PTB sputum smear is positivesputum smear is positive PTB with cavitary lesions- repeated negativePTB with cavitary lesions- repeated negative sputum smears – diagnosis to be changedsputum smears – diagnosis to be changed
  24. 24. D/D of CXR finding associated with PTB-D/D of CXR finding associated with PTB- 1.Cavitation-1.Cavitation- Infection- pneumoniaInfection- pneumonia lung abscesslung abscess fungal infectionfungal infection Non-infectious- bronchogenic carcinomaNon-infectious- bronchogenic carcinoma connective tissue diseaseconnective tissue disease occupational lung diseaseoccupational lung disease 2.Unilateral infiltration-2.Unilateral infiltration- pneumoniapneumonia bronchogenic cabronchogenic ca 3.Bilateral infiltration-3.Bilateral infiltration- pneumoniapneumonia connective tissue diseaseconnective tissue disease sarcoidosissarcoidosis 4.Mediastinal lymphadenopathy-4.Mediastinal lymphadenopathy- lymphomalymphoma bronchogenic cabronchogenic ca sarcoidosissarcoidosis
  25. 25. Diagnosis of extra pulmonary TBDiagnosis of extra pulmonary TB-- Mainly by HPE (histopathology examination)Mainly by HPE (histopathology examination) TB lymphadenitis-TB lymphadenitis- presence of caseationpresence of caseation TB meningitis-TB meningitis- CSF examinationCSF examination CSF pressure highCSF pressure high clear & cloudyclear & cloudy increase in WBC count withincrease in WBC count with lymphocyte predominantlymphocyte predominant CSF protein,CSF protein, ↓↓ glucoseglucose
  26. 26. Tuberculin skin testTuberculin skin test-- Tuberculin-purified protein derived from tubercleTuberculin-purified protein derived from tubercle bacillibacilli Purified protein derivative (PPD)Purified protein derivative (PPD) Injected intradermallyInjected intradermally Induration read after 48 hrs.Induration read after 48 hrs. Hypersensitivity reactionHypersensitivity reaction Positive Tuberculin test- indicates infectionPositive Tuberculin test- indicates infection Positive tuberculin test- induration > 10mmPositive tuberculin test- induration > 10mm Negative tuberculin test- induration < 10mmNegative tuberculin test- induration < 10mm A positive tuberculin test is only one pieceA positive tuberculin test is only one piece evidence in favour of dignosis of Tuberculosisevidence in favour of dignosis of Tuberculosis

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