Pathology of tuberculosis and fungal infections
Where does TB typically implant?
1. Lower part of upper lobe. 2. Upper part of lower lobe (close to pleura).
Complications of Secondary Pulmonary tuberculosis
1. Progressive pulm. tuberculosis. 2. Erosion into bronchi with cavitation. -can lead to hemoptysis. 3. Miliary pulmonary disease. 4. Pleural effusion/tuberculous empyema. 5. Endobronchial, endotracheal, laryngeal tuberculosis. 6. Systemic miliary tuberculosis. 7. Isolated-organ tuberculosis (incl tub. meningitis. 8. Lymphadenopathy (usually in cervical region).
Two main pathologic features of TB (caused by tissue hypersensitivity)
1. Tissue cavitation. 2. Caseous necrosis.
What can cause necrotizing granulomatous inflammation?
1. Tuberculosis. 2. Fungal infection. (consider sarcoidosis in differential) .
Caseous necrosis
A "cheesy"-like appearance to granulomas: -caused by M. tuberculosis infection.
Progressive primary tuberculosis
A development into disease with no interruption, usually in those with compromised immune systems: -e.g. malnourishment, elderly, AIDS, racial groups like the Inuit. -may result in miliary and tuberculous meningitis.
Nontuberculous mycobacterial disease
A tuberculosis-like disease that affects immunocompetent host. -presents as upper lobe cavitary disease. -usually assoc. w. long history of smoking or alcoholism.
TB infects which types of cells?
Alveolar macrophages.
Ghon focus
Area of sensitization in the lung: -a 1-1.5 cm grey-white consolidation. -undergoes caseous necrosis.
Secondary tuberculosis
Arises from reactivation of dormant primary lesions: -usually many decades after initial infection. -particularly when host resistance is weakened. -also can result from exogenous re-infection.
Which organism exhibits broad based budding on periodic acid schiff staining?
Blastomyces.
Transmission of TB
By inhalation of: 1. Airborne organisms in aerosols of infected. 2. Exposure to aerosolized contaminated secretions.
Macroscopic appearance of TB-diseased tissue
Caseation necrosis.
Immune response to TB
Cell-mediated immunity confers resistance. -results in tissue hypersensitivity to tubercular antigens.
Which organisms stains mucicarmine positive?
Cryptococcus.
Primary Tuberculosis
Development of tuberculosis in previously unexposed person. -source of organism is exogenous.
MAC presentation
Disseminated disease with systemic symptoms: -fever, night sweats, weight loss. -hepatosplenomegaly, lymphadenopathy. -GI (diarrhea, malabsorption). -Pulmonary involvement similar to TB. -Foamy, stuffed macrophages. -no granulomas.
Fungal infections of lung: -form fungal spores
Five: 1. Blastomyces dermatidis (central Can/USA). 2. Histoplasma capsulatum (central Can/USA). 3. Coccidiodes immitis (Southwest USA). 4. Cryptococcus neoformans (ubiquitous). 5. Cryptococcus gattii (BC).
Factors that worsen TB prognosis
Four: 1. Age. 2. Debillitated. 3. Immunocompromised. 4. MDR-TB.
Main types of Mycobacterium tuberculosis
Four: 1. M. tuberculosis --> human. 2. M bovis --> Bovine tubercle bacillus. 3. M. africanum --> African tubercle bacillus. 4. M. microti --> Vole tubercle bacillus.
Pathology of fungal infections: Hyphae forming
Four: 1. Necrotizing pneumonia. 2. Propensity for blood vessel invasion (angioinvasion). 3. Consequent tissue infarction. 4. Systemic dissemination (esp. to brain).
What population does MAC primarily affect?
HIV positive: -especially when CD4 < 100cells/mm3.
Reservoir of TB
Humans with infection or disease.
What organism causes TB?
Mycobacterium tuberculosis.
Microscopic appearace of TB-diseased tissue
Necrotizing granulomatous inflammation.
Cavitation in secondary tuberculosis
Occurs readily in secondary form. -results in dissemination along airways. -increases infectivity.
Role of tissue hypersensitivity in TB
Pathologic features of TB the result of destruction of host tissue by host immune response.
What happens to Ghon complex post-infection?
Progressive fibrosis, followed by radiologically detectable calcification.
Differentation of TB from fungal infection of lungs
Requires identification of organism of tissue.
Multidrug resistance tuberculosis
Resistance of mycobacteria to two or more of the primary drugs used for tx.
Hallmark for TB infection in lungs
Seeding of a focus with organisms.
Granulomas: TB vs. NonTB mycobacterial disease.
TB typically presents with granulomas, while NonTB mycobacterial disease does not.
Endosomal manipulation
TB's affect on alveolar macrophage: 1. Maturation arrest. 2. Lack of acid pH. 3. Ineffective phagolysosome formation.
Ghon complex.
The combination of parenchymal lesion and regional node involvement. -regional lymph nodes also contain tubercle bacilli, and will caseate.
Fungal infections of lung: -form fungal hyphae
Three: 1. Aspergillus. 2. Candida. 3. Mucor. -do not form granulomas.
Nontuberculous mycobacterial disease: Strains
Three: 1. Mycobacterium avium complex. 2. M. kansasii. 3. M. abcessus.
Most common cause of death from single infectious agent.
Tuberculosis: -1.7 billion individuals infected worldwide.
Sarcoidosis
Unknown etiology: -non-caseating, non-necrotizing granulomas. -major differential of infectious granulomatous inflammation. -a diagnosis of exclusion (if no nodule/sign of organism, then sarcoidosis).
Typical location of secondary pulmonary tuberculosis
Usually localized to: -Apex of one or both upper lobes. -may relate to high oxygen tension in apices.
Seeding location for TB
Usually two: -lungs. -regional lymph nodes.
Pathological/radiology features of Fungal infection (spore forming)
Very similary to tuberculosis: -granulomatous inflammation with necrosis. -disseminated miliary disease.
