Tuberculosis (TB) Overview

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Questions and Answers

Which of the following statements accurately describes primary progressive tuberculosis?

It primarily affects the gastrointestinal system.

It presents with chronic respiratory failure only.

It is characterized by significant disease progression in older adults and immunosuppressed individuals. (correct)

It occurs in 95% of all newly infected individuals.

What is the principal source of transmission for tuberculosis?

Environmental exposure to soil and dust

Vector-borne transmission through insects

Person-to-person airborne organisms from active cases (correct)

Contaminated food and water

Which risk factor is considered the greatest for progression to active tuberculosis disease?

Immunosuppression (correct)

Overcrowding

Malnutrition

Alcoholism

Which complication is least likely to be associated with primary progressive tuberculosis?

Cavitary lung lesions Signup and view all the answers

What typical clinical presentation is associated with primary tuberculosis in most individuals?

Asymptomatic with possible fever and pleural effusion Signup and view all the answers

Which of the following is a major consequence of primary progressive tuberculosis?

Systemic miliary tuberculosis Signup and view all the answers

In individuals with secondary tuberculosis, what is the typical pattern of disease that is observed?

Apical disease with cavitation Signup and view all the answers

Which of the following conditions is frequently seen as a presentation of extra-pulmonary tuberculosis?

Cervical lymphadenopathy (scrofula) Signup and view all the answers

Which of these factors does NOT typically contribute to the development of tuberculosis?

Exposure to high altitudes Signup and view all the answers

What is the characteristic finding for individuals with primary tuberculosis?

Fibrocalcific pulmonary nodule (Ranke complex) Signup and view all the answers

What is the main distinguishing feature of a Ghon complex in primary tuberculosis?

It is characterized by caseous necrosis in the center. Signup and view all the answers

Which method allows for the rapid diagnosis of active tuberculosis?

PCR amplification of M.tuberculosis DNA. Signup and view all the answers

What aspect differentiates the lymphadenitis in HIV-positive individuals from those who are HIV-negative?

It tends to be multifocal in HIV-positive individuals. Signup and view all the answers

What is the role of antibiotic susceptibility testing in tuberculosis treatment?

It can only be performed by culture methods. Signup and view all the answers

What signifies the absence of granulomas in tissues of HIV-positive tuberculosis patients?

They have a more aggressive disease course. Signup and view all the answers

Which of the following statements regarding the morphology of primary tuberculosis is correct?

Caseating granulomas are characteristic of this stage. Signup and view all the answers

What specific change occurs to the Ghon focus as the immune response enhances in primary tuberculosis?

It undergoes calcification and fibrosis. Signup and view all the answers

What is a likely complication of intestinal tuberculosis?

Formation of strictures in the ileum. Signup and view all the answers

What best describes the importance of culture in tuberculosis diagnosis?

It remains the gold standard for confirming active infection. Signup and view all the answers

Study Notes

Tuberculosis (TB)

Definition: A chronic pulmonary and systemic disease caused by Mycobacterium tuberculosis (acid-fast bacilli).
Transmission: Person-to-person transmission of airborne organisms from an active case to a susceptible host. Mycobacterium bovis can also cause oropharyngeal and intestinal TB, typically from unpasteurised milk.

Risk Factors

Poverty and Overcrowding: High-risk environments include prisons, homeless shelters, and long-term care facilities.
Immigration: Individuals from high-burden TB countries have an increased risk.
Malnutrition: Malnourished individuals are more susceptible.
Alcoholism: Alcohol abuse is linked to TB risk.
Immunosuppression: Conditions like AIDS, use of TNF inhibitors, organ transplantation, and glucocorticoid use weaken the immune system, increasing risk.
Chronic Debilitating Illnesses: Diabetes, Hodgkin lymphoma, chronic lung disease (silicosis), and chronic renal failure increase vulnerability.
Greatest progression risk: AIDS.

Types of Tuberculosis

Primary Tuberculosis

Occurs in individuals previously unexposed.
Primarily asymptomatic or presents with fever +/- pleural effusion (95% of cases).
Earliest evidence of infection is a small fibrocalcific pulmonary nodule at the infection site (Ranke complex).
Source of infection is typically exogenous (external source).
Primary Progressive Tuberculosis: In 5% of newly infected individuals, progressive disease develops. Symptoms resemble acute bacterial pneumonia with consolidation, adenopathy, and effusion. More likely in older or immunocompromised individuals.
Complications: Possible haematogenous or lymphatic dissemination, potentially leading to systemic miliary TB (lungs, liver, bone marrow, etc.), tuberculous meningitis, pleural effusions, tuberculous empyema, obliterative fibrous pleuritis, Pott disease (vertebral TB), and lymphadenitis (most common extra-pulmonary presentation, often cervical "scrofula").

Secondary Tuberculosis

Develops in a previously sensitised host.
Commonly caused by reactivation of latent infection, or exogenous reinfection.
Reactivation is more common in low-prevalence areas, while re-infection is more common in high-contagion areas.
Typically apical disease with cavitation. Lymph nodes less involved initially compared to primary TB.
Classic symptoms: Malaise, anorexia, weight loss, fever, night sweats, haemoptysis, pleuritic chest pain.

Diagnosis

Acute Infection

Sputum Smears and Cultures: Acid-fast bacilli smears and culture of sputum used; culture takes 3-6 weeks on solid media, and 2 weeks on liquid media.
Antibiotic Susceptibility testing: Only possible via culture.
Molecular Diagnosis: PCR amplification for rapid diagnosis is gaining importance, though still considered secondary to culture.
Culture remains the gold standard due to accurate results and ability to track antibiotic effectiveness. PCR used when quick results are critical.

Latent Infection

IFN-γ release assays (IGRAs): Blood test to detect immune response.
Tuberculin Skin Test (TST): Using purified protein derivative (PPD) to test for exposure to M. tuberculosis.

Histological and Morphological Features

Histology: Formation of caseating granulomas with multinucleated giant cells.
Primary TB Morphology: Infection in the lower part of the upper lobe or upper part of the lower lobe; characteristic Ghon focus (small area of inflammation, caseous necrosis) and draining to regional lymph nodes (forming the Ghon complex where lung lesion & regional nodes combine). This combination often calcifies (Ranke complex) and is the classic manifestation of healed primary TB.
Secondary TB Morphology: Focal consolidation (up to 2cm) often near the apical pleura.
Intestinal TB: Usually due to ingesting contaminated, raw milk containing M. bovis. Can cause strictures of the ileum.
Atypical Features (HIV-positive cases): Variable pulmonary manifestation, often focal/multifocal infiltrates; increased false-negatives in sputum smears and skin tests; absence of granulomas; and frequent extrapulmonary involvement. Lymphadenitis is often multifocal in HIV-positive, unlike unifocal/localized nodes seen in HIV-negative cases.

Treatment

Multi-drug regimen: At least four drugs are necessary due to the potential for multi-drug resistant TB.

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Description

This quiz provides an overview of tuberculosis, focusing on its definition, transmission methods, and various risk factors. Learn about how conditions such as poverty, malnutrition, and immunosuppression contribute to increased susceptibility to TB. Test your knowledge on this significant public health issue.