Cause Caused by Mycobacterium tuberculosis (M. tuberculosis) Gram (+) rod (bacilli). Acid-fast Pulmonary TB occurs in the lungs 85% of all TB cases are pulmonary Extrapulmonary TB occurs in places other than the lungs, including the: Larynx Lymph nodes Brain and spine Kidneys Bones and joints Miliary TB occurs when tubercle bacilli enter the bloodstream and are carried to all parts of the body
Transmission Spread person to person through airborne particles that contain M. tuberculosis Transmission occurs when an infectious person coughs, sneezes, laughs, or sings Prolonged contact needed for transmission 10% of infected persons will develop TB disease at some point in their lives 5% within 1-2 years 5% at some point in their lives Reactivation due to immune suppression Infects 1/3 rd of the world’s population Chance of death: 4% 2 nd most common cause of death from an infectious disease in the world. Causing 1.2-145 million deaths a year
Pulmonary Tuberculosis Primary pulmonary TB (primary exposure) is characterized by the Ghon complex and consists of 1.) subpleural (fissure) focus of inflammation. 2.) Infected (inflamed) lymph nodes draining the primary, subpleural lesion. A Ghon focus is a primary lesion usually subpleural, often in the mid to lower zones Secondary pulmonary TB (reactivation) is characterized by a focus of infection and granuloma formation usually in the apex of the lung. The small granulomas (tubercles) eventually coalesce to form larger areas of consolidation with central caseating necrosis. Regional lymph nodes contain caseating granulomas. Progressive pulmonary TB: Primary or secondary TB may go on to heal. Caseating granulomas are replaced by fibrosis and calcification. Cases that don’t heal spontaneously or with drug therapy can progress to form cavities or spread to other parts of the lung and to other organs through lymphatic channels and bloodstream. Milliary tuberculosis.
Risk Factors HIV 30% develop active disease. Disease of poverty: Linked to malnutrition and overcrowding. Drugs: Injection Prisons, homeless centers High risk ethnic minorities, healthcare workers Smoking, diabetes mellitus, alcoholism
Signs/Symptoms Productive prolonged cough * Chest pain Hemoptysis Fever and chills Night sweats Fatigue Loss of appetite Weight loss
Diagnosis Medical history Physical examination Mantoux tuberculin skin test Chest x-ray: Consolidation or cavitation in lung apices. Sputum Collection: essential to confirm TB Culture: 2-8 week Smear, PCR
Treatment Latent infection: Daily Isoniazid therapy for 9 months Monitor patients for signs and symptoms of hepatitis and peripheral neuropathy Alternate regimen – Rifampin for 4 months TB Disease: Regimen of 3-4 drugs 1 st -line drugs for 6 months. Isoniazid (INH) Rifampin (RIF) Pyrazinamide (PZA) Ethambutol (EMB) Recurrent Disease: Test for antibiotic susceptibility and if MDR-TB, treat with at least 4 effective antibiotics for 18-24 months. Primary vs Secondary resistance Prevention: BCG vaccine for children
Case A 23-year-old man presented with a 4-week history of coughing, breathlessness and malaise. He had lost 4kg in weight, but had no history of night sweats or haemoptysis. He had returned from holiday in Pakistan 2 months earlier. On examination, he was mildly pyrexial (37.8°C) but had no evidence of anaemia or clubbing. Crepitations were audible over the lung apices; there were no other physical signs. The chest X-ray showed bilateral upper- and middle-lobe shadowing but no hilar enlargement. Sputum was found to contain acid-fast bacilli and Mycobacterium tuberculosis was subsequently cultured. A Mantoux test was strongly positive. A diagnosis of pulmonary tuberculosis was made. The patient was treated with isoniazid and rifampicin for 6 months, together with pyrazinamide for the first 2 months. He was allowed home on chemotherapy when his sputum became negative on direct smear. The chest X-ray is now much improved.
References 1. http://radiopaedia.org/cases/pulmonary-tuberculosis 1. http://radiopaedia.org/cases/pulmonary-tuberculosis 2. http://library.med.utah.edu/WebPath/LUNGHTML/LUNG033.ht ml http://library.med.utah.edu/WebPath/LUNGHTML/LUNG033.ht ml 3. http://www.pathpedia.com/education/eatlas/imagepedia/pulm onary_tuberculosis-necrotizing_granuloma.aspx http://www.pathpedia.com/education/eatlas/imagepedia/pulm onary_tuberculosis-necrotizing_granuloma.aspx