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.