Amr El Said


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Amr El Said

  1. 1. General Considerations : <ul><li>Tuberculosis is a chronic infection, potentially of lifelong duration </li></ul><ul><li>In the past , tuberculosis has been called consumption , because it seemed to consume people from within, with a bloody cough , fever, pallor , and long relentless wasting. TB is also called Koch's disease after the scientist Robert Koch </li></ul><ul><li>Tuberculosis continues to be a problem major health worldwide </li></ul>
  2. 2. Etiology: <ul><li>It grows slowly and differs form other mycobacteria by its ability to produce niacin. </li></ul><ul><li>Mycobacterium T. hominis: is the causative organism of pulmonary tuberculosis. </li></ul><ul><li>M. avium-intracellulare (MAIK): seen in immunocompromised hosts (particularly in persons with AIDS </li></ul>
  3. 3. Mode of transmission <ul><li>by inhalation of the tubercle bacilli of the human type present in the sputum expectorated by a patient with an open pulmonary tuberculous lesion. </li></ul>
  4. 4. Pathogenesis: <ul><li>About 90% of those infected with Mycobacterium tuberculosis have asymptomatic , latent TB infection (sometimes called LTBI), with only a 10% lifetime chance that a latent infection will progress to TB disease. However, if untreated, the death rate for these active TB cases is more than 50%. </li></ul><ul><li>Tuberculosis is classified into primary and secondary tuberculosis: </li></ul>
  5. 5. 1- Primary pulmonary tuberculosis <ul><li>Primary Tuberculosis is an infection of persons who have not had prior contact with the tubercle bacillus. Inhaled bacilli are commonly deposited in alveoli immediately beneath the pleura, usually in the lower part of the upper lobes or the upper part of the lower lobes. </li></ul>
  6. 6. Primary pulmonary tuberculosis <ul><li>Within the granuloma, T lymphocytes (CD4+) secrete cytokines such as interferon gamma, which activates macrophages to destroy the bacteria with which they are infected T lymphocytes (CD8+) can also directly kill infected cells. Importantly, bacteria are not always eliminated within the granuloma, but can become dormant, resulting in a latent infection. Another feature of the granulomas of human tuberculosis is the development of cell death, also called necrosis, in the center of tubercles. To the naked eye this has the texture of soft white cheese and was termed caseous necrosis. </li></ul>
  7. 7. Macroscopic picture: <ul><li>The primary infection characteristically produces a “Ghon complex” formed of : </li></ul><ul><li>1- Ghon focus : small area of pneumonic consolidation about 1-3cms in diameter, sub- pleural in location present in the base of the upper lobe or apex of lower lobe. </li></ul><ul><li>2- Tuberculous lymphangitis : of the draining lymphatic channels. </li></ul><ul><li>3- Tuberculous lymphadenitis : of the tracheobronchial nodes which are enlarged, matted together and their cut surface show areas of caseous necrosis. </li></ul>
  8. 8. Ghon Complex
  9. 9. Microscopic picture: <ul><li>The Ghon focus consists of a central area of pink caseous necrosis surrounded by inflammatory infiltrate and walled of by an area of granulation tissue containing multinucleated Langhan's giant cells. </li></ul>
  10. 10. Epitheloid cells in Granuloma
  11. 11. Fate of primary tuberculosis: This is depends on : <ul><li>Virulence of the organism. </li></ul><ul><li>Dose of the infection. </li></ul><ul><li>Degree of resistance of the host. </li></ul><ul><li>1-If patient resistance is good and the organis is of low virulence, Ghon complex undergo healing and over time usually evolve to fibrocalcific nodules. </li></ul><ul><li>2-If the patient resistance is poor and/or the organism of high virulence , Progressive primary tuberculosis will develop: </li></ul><ul><li>The primary Ghon focus in the lung enlarges rapidly, erodes the bronchial tree, and spreads, a sequence that results in adjacent “satellite” lesions. </li></ul>
  12. 12. <ul><li>And spread of infection will take place by : </li></ul><ul><ul><li>Local spread: to the surrounding lung tissue and pleura. </li></ul></ul><ul><ul><li>Lymphatic spread: along bronchi, leading to tuberculous bronchopneumonia. </li></ul></ul><ul><ul><li>Haematogenus spread: leading to military tuberculous or isolated organ tuberculosis or miliary tuberculosis in the lung. </li></ul></ul>
  13. 13. 2- Secondary pulmonary tuberculosis: <ul><li>Secondary (cavitary) tuberculosis usually results from reactivation of dormant, endogenous tubercle bacilli in a sensitized patient who has had previous contact with the tubercle bacillus. In some cases, the disease is caused by reinfection with exogenous bacilli. The lesion begins as a tubercle, the microorganisms searching for high oxygen tension; usually settle in the apical portion of one or both lungs. </li></ul>
  14. 14. <ul><li>A tubercle is no larger than 3cm and consists of a central area of caseous necrosis surrounded by granulomatous tissue containing the typical Langhans giant cells and the epithelioid cells. The tubercle is separated from the surrounding tissue by a layer of fibrous tissue infiltrated with lymphocytes </li></ul>
  15. 15. Fate of secondary pulmonary tuberculosis: <ul><li>Healing by fibrosis with dystrophic calcification occurs in the most cases when the dose of infection is small, virulence of the organism is low and patient resistance is good. </li></ul><ul><li>Spread of infection occurs when the patient resistance is poor and the virulence of the organism is high. Spread occurs directly, by lymphatic, natural passages or blood stream. </li></ul><ul><li>Fibrocaseous tuberculosis with cavitation occurs with moderate dose of organism and moderate resistance of the patient. </li></ul>
  16. 16. Fibrocaseous tuberculosis with cavitation <ul><li>The cavity is chronic with fibrotic walls lined by caseous material and is traversed by blood vessels and bronchi. The surrounding lung tissue shows multiple focal areas of caseation and other cavities. </li></ul>
  17. 17. Complications of Fibrocaseous tuberculosis: <ul><li>1- Spread to the pleura causing: pleural effusion, fibrinous pleurisy, tuberculous empyema, pneumothorax and pyopneumothorax. </li></ul><ul><li>2- Coughing of the content of the cavity lead to: Tuberculous tracheobronchitis, tuberculous laryngitis, tuberculous glossitis, and tuberculous enteritis. </li></ul><ul><li>3- Erosion of the traversing blood vessels lead to : Hemoptysis, Haematogenus spread. </li></ul><ul><li>4- Secondary amyloidosis </li></ul>
  18. 18. Miliary Tuberculosis: <ul><li>Miliary tuberculosis is the disseminated form of tuberculosis and is caused by seeding of the bacilli through lymphatics or blood vessels. </li></ul><ul><li>Gross picture: </li></ul><ul><li>Minute, yellow-white lesions resembling millet seeds (hence military). </li></ul><ul><li>Sites: </li></ul><ul><li>The lung, lymph nodes, kidneys, adrenals, bone marrow, spleen, liver, meninges, brain, eye grounds, and genitalia are common sites of miliary lesions. </li></ul><ul><li>Fates: </li></ul><ul><li>All granulomas have similar features and follow the same progression, namely focal collections of histiocytes, followed by epithelioid cells, Langhan’s giant cells, central caseation necrosis and eventually fibrosis and mineralization. </li></ul>
  19. 19. Miliary Tuberculosis:
  20. 20. Miliary Tuberculosis:
  21. 21. Diagnosis of pulmonary tuberculosis: <ul><li>A- Radiology </li></ul><ul><li>The following characteristics of a chest radiograph favour the diagnosis of tuberculosis: </li></ul><ul><li>(1). shadows mainly in the upper zone; </li></ul><ul><li>(2).patchy or nodular shadows; </li></ul><ul><li>(3).the presence of a cavity or cavities, although these, of course, can also occur in lung abscess, carcinoma, etc; </li></ul>
  22. 22. <ul><li>(4).the presence of calcification, although a carcinoma or pneumonia may occur in an areas of the lung where there is calcification due to tuberculosis; </li></ul><ul><li>(5).bilateral shadows, especially if these are in the upper zones; </li></ul><ul><li>(6).the persistence of the abnormal shadows without alteration in an x-ray repeated after Several weeks; this helps to exclude a diagnosis of pneumonia or other acute infection . </li></ul>
  23. 25. B-Laboratory <ul><li>(1). Direct smear examination is only positive when large numbers of bacilli begin to be excreted, so that a negative smear by no means excludes tuberculosis. A negative smear in the presence of extensive disease and cavitation makes the diagnosis less likely, particularly if the negatives are frequently repeated. </li></ul>
  24. 26. <ul><li>(2). Tuberculin testing: </li></ul><ul><li>A positive tuberculin test although it is of great use in children, has limited diagnostic significance in older age groups. The tuberculin test in complished with old tuberculin (OT) and purified protein derivative (PPD) of tuberculin that is a crude culture filtrate of M.tuberculosis. </li></ul><ul><li>OT and PPD dilute 0. 1 ml (unit and content) </li></ul>
  25. 27. Differential Diagnosis: <ul><li>Although tuberculosis may be confused with virtually any intrathoracic condition, certain diseases are frequently considered in differential diagnosis. </li></ul><ul><li>(1). bronchiectasis may present with symptoms sugesting tuberculosis. And bronchiectatic and emphysematous areas surrounded by infiltrate may mimic cavitation roentgenographically. </li></ul>
  26. 28. Differential Diagnosis: <ul><li>(2). Cavitary lung abscess often involves the dorsal segments of the lower lobes and posterior segments of the upper lobes. Typically lung abscess causes little in the way of physical findings, may have a fluid level, and is not associated with patchy bronchogenic infiltrates, in contrast, physical findings are prominent over tuberculous cavities, fluid levels are rare. and patchy infiltrates elsewhere are the rule. </li></ul><ul><li>(3).Acute bacterial pneumonias may resemble florid tuberculosis in all particularsexcept for the sputum examination and response to antimicrobial drugs. </li></ul>
  27. 29. Differential Diagnosis: <ul><li>(4). Neoplasm may resemble tuberculosis, as in an isolated coin lesion. An obstructing and inconspicuous endobronchial tumor causing distal chronic inflammation or a caviting neoplastic mass. (An irregular cavity wall suggests necorotic neoplasm.) </li></ul>
  28. 30. Treatment:
  29. 31. Treatment: <ul><li>Treatment for TB uses antibiotics to kill the bacteria. </li></ul><ul><li>The two antibiotics most commonly used are rifampicin and isoniazid . However, instead of the short course of antibiotics typically used to cure other bacterial infections, TB requires much longer periods of treatment (around 6 to 12 months) to entirely eliminate mycobacteria from the body. </li></ul><ul><li>Latent TB treatment usually uses a single antibiotic, while active TB disease is best treated with combinations of several antibiotics, to reduce the risk of the bacteria developing antibiotic resistance . </li></ul><ul><li>People with latent infections are treated to prevent them from progressing to active TB disease later in life. </li></ul>
  30. 32. Prevention:
  31. 33. <ul><li>The World Health Organization (W.H.O.) declared TB a global health emergency in 1993, and the Stop TB Partnership developed a Global Plan to Stop Tuberculosis that aims to save 14 million lives between 2006 and 2015. </li></ul><ul><li>Since humans are the only host of Mycobacterium tuberculosis, eradication would be possible: a goal that would be helped greatly by an effective vaccine. </li></ul>
  32. 34. TB prevention and control takes two parallel approaches. In the first, people with TB and their contacts are identified and then treated. In the second approach, children are vaccinated to protect them from TB
  33. 35. Vaccines: <ul><li>Many countries use Bacillus Calmette-Guérin (BCG) </li></ul><ul><li>Several new vaccines to prevent TB infection are being developed: </li></ul><ul><li>Recombinant tuberculosis vaccine rBCG30 </li></ul><ul><li>DNA TB vaccine </li></ul>