PULMONARY TUBERCULOSIS Year 4 Paediatrics Notes OmpathStudy

PULMONARY TUBERCULOSIS Year 4 · Paediatrics Collection: 4TH YEAR ALL NOTES / PAEDS / PAEDS 4.1 / Agisa -- Slide 1 Pulmonary tuberculosis mbchb4 Slide 2 aetiology TB is caused by the bacterium Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis and seven very closely related mycobacterial species (M. bovis, M. africanum, M. microti, M. caprae, M. pinnipedii, M. canetti and M. mungi) together comprise what is known as the M. tuberculosis complex. Slide 3 The agent: Mycobacteria sp. Actinobacteria (Phylum), family Mycobacteriaceae Genus Mycobacteria Species are described in several major groups for purpose of diagnosis and treatment: M. tuberculosis, M. bovis, M. africanum, and M. microti; – M. leprae which causes Hansen’s disease or leprosy; – Nontuberculous mycobacteria (NTM) are all the other mycobacteria which can cause pulmonary disease resembling tuberculosis, lymphadenitis, skin disease, or disseminated disease. Slide 4 Global burden 22 countries have 80% of TB cases today (tbalert.com) Slide 5 Kenya is among high TB burden countries Slide 6 transmission M. tuberculosis is transmitted through airborne infectious droplet nuclei which are generated when persons who have pulmonary or laryngeal TB disease cough, sneeze, shout, or sing.\nThese tiny particles (1– 5 microns in diameter) can remain suspended in the air for several hours.\nTransmission occurs when a person inhales droplet nuclei containing M. tuberculosis, and the droplet nuclei traverse the mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli of the lungs. Slide 7 Risk factors of exposure to the TB bacillus Incidence of infectious TB in population/community Average duration of infectiousness of cases Number of cases/contact interactions over time Population density Family size Poverty\nOvercrowding Slide 8 Risk factors for transmission 1.Level of TB infection in a person: A person with TB who expels more bacilli is more infectious than one who expels fewer bacilli. The level of infection is increased if the patient has a cough or pulmonary disease, poor cough etiquette, inappropriate treatment, cavitatory disease, culture or bacteriologically positive disease. 2. Susceptibility of the exposed child with the contact: This is dependent on the immune status of the exposed child. If the child contact has a weakened immune system, TB transmission is more likely. The very young have a higher risk of developing disease upon exposure. Slide 9 3. Environmental factors: These are factors that may increase the concentration of the bacilli in the immediate environment of the child. They include the concentration of infectious droplet nuclei in the air, exposure in small-enclosed spaces, recirculation of air containing infectious droplet nuclei, improper specimen handling procedures that generate infectious droplet nuclei. 4. Proximity, frequency and duration of exposure with the infectious person: The longer the duration of contact, the more frequent the contact, the closer the contact, the higher the risk of transmission Slide 10 Pathogenesis of pulmonary tuberculosis Upon exposure to an infectious case, the child inhales droplet nuclei containing infectious bacilli and they reach the alveoli. They are ingested by alveolar macrophages which destroy them. A few bacilli may survive, multiply in the macrophages and are released when the macrophages die. This process induces an immune response.\nThe immune cells in the alveoli may form an immune capsule called a granuloma (Ghon focus) that keeps the bacilli contained and under control. It might also involve the draining lymph nodes. Both the granuloma and the draining lymph nodes are called Ghon complex (Primary complex). If this is present without signs and symptoms of disease, it is latent TB infection. Slide 11 pathogenesis If the immune system cannot keep the bacilli under control, they multiply rapidly, affecting the lung parenchyma and the airways. They may spread through the lymphatics or the blood stream to the rest of the body. The child will then be symptomatic and said to be having TB disease (primary TB disease). Without treatment, many children infected with M. tuberculosis will develop TB disease in the first or second year after infection. In others, the bacilli remain dormant for a long time and they may develop TB disease at some point in their lifetime. Progression of the latent infection to disease is secondary TB disease. Slide 12 pathogenesis Progression of the primary complex may lead to enlargement of hilar and mediastinal nodes with resultant bronchial collapse.\nProgressive primary TB disease may develop when the primary focus cavitates and organisms spread through contiguous bronchi.\nLympho-haematogenous dissemination, especially in children, may lead to milliary TB when caseous material reaches the bloodstream from a primary focus or a caseating metastatic focus in the wall of a pulmonary vein.\nTB meningitis may result from haematogenous dis