1
Q
How does the pathogen Mycobacterium tuberculosis primarily enter the body during a TB infection?
A
Answer:
Mycobacterium tuberculosis primarily enters the body through inhalation, as it is an airborne pathogen that makes its way into the respiratory tract and bronchial system.
2
Q
What happens when macrophages encounter Mycobacterium tuberculosis?
A
Answer:
* When macrophages encounter Mycobacterium tuberculosis, they engulf the pathogen through phagocytosis and attempt to put it into a phagosome.
- However, tuberculosis can inhibit the phagolysosome, preventing the breakdown of the pathogen.
- As a result, the Mycobacterium multiplies within multiple macrophages.
3
Q
Which cytokines are released by macrophages during a TB infection, and what is their effect?
A
Answer:
* Macrophages release cytokines such as
1. IL-1,
2. . IL-6,
3. . TNF-α during a TB infection.
- These cytokines attract more macrophages and lymphocytes to the area, leading to the formation of caseating granulomas.
4
Q
Describe the formation of a caseating granuloma during primary TB infection.
A
Answer:
* The caseating granuloma usually forms within the right middle and lower lobe due to exposure to Mycobacterium tuberculosis.
- The pathogen multiplies within macrophages, leading to the release of cytokines and attracting more macrophages and lymphocytes.
- This immune response results in the formation of a caseating granuloma with central necrosis, surrounded by more macrophages and T lymphocytes.
5
Q
What is the Ghon complex, and what causes its formation during primary tuberculosis?
A
Answer:
- The Ghon complex is a combination of a Ghon focus (caseating granuloma) forming in the middle or lower lobe, close to the pleura, and hilar lymphadenopathy granuloma forming in a nearby lymph node.
- It occurs as a result of the body’s attempt to wall off and protect against the spread of Mycobacterium tuberculosis.
6
Q
What role do T cells play in the immune response to tuberculosis?
A
Answer:
* T cells release IFN-γ (Interferon-gamma) during a TB infection.
- IFN-γ stimulates more macrophages to come to the area and form granulomas, as well as recruit additional macrophages and T cells to help contain and control the Mycobacterium infection.
7
Q
Why is the detection of IFN-γ important for TB diagnostics?
A
Answer:
- The detection of IFN-γ is important for TB diagnostics because it is a key immune response marker specific to Mycobacterium tuberculosis infection.
- Measuring IFN-γ levels can aid in diagnosing TB and differentiating it from other respiratory conditions.
8
Q
What is the primary risk factor for a patient to develop primary TB with a Ghon complex?
A
Answer:
- exposure to Mycobacterium tuberculosis.
- They must come into contact with the bacterium to contract the infection.
9
Q
Name some patient populations at a higher risk of exposure to tuberculosis.
A
Answer :
- Prisoners
- Healthcare workers
- . Homeless individuals
- Immigrants coming from regions with a high prevalence of TB
- Intravenous (IV) drug abusers
10
Q
What does exposure to TB mean for individuals at risk?
A
Answer:
* means that individuals are at risk of acquiring the infection.
- However, exposure alone does not guarantee the development of active TB disease.
- Some individuals may clear the pathogen or enter a latent phase, while others may progress to active TB over time.
11
Q
What happens after a patient acquires primary TB infection?
A
Answer:
they may enter a latent phase or develop primary progressive tuberculosis.
- Latent Phase: This occurs in over 90% of cases, during which the immune system contains the infection, and the individual does not show any symptoms. However, the bacteria remain dormant and can reactivate later, leading to secondary tuberculosis.
- Primary Progressive Tuberculosis: This occurs in less than 10% of cases, where the disease continues to worsen, causing more damage to the lung tissue.
- It’s important to note that not all individuals exposed to TB will progress to active disease; many may remain asymptomatic or control the infection in a latent state.
12
Q
What happens to the Ghon complex in most cases of latent TB, and how does the immune system respond to the infection in these cases?
A
Answer:
* In over 90% of cases of latent TB, the Ghon complex undergoes fibrocalcification, resulting in a Ranke complex.
- The immune system effectively walls off the tuberculosis, keeping it in a dormant, shut-down state.
- Fibrocalcification and immune control prevent the bacteria from multiplying, dividing, destroying lung tissues, and causing symptoms.
13
Q
How does immunosuppression impact latent TB, and what patient populations are at high risk of reactivation or progression to active TB?
A
Answer:
Immunocompromised individuals, such as those with HIV, post-transplant patients, those on immunosuppressive medications, individuals with diabetes mellitus and chronic kidney disease, alcoholics, malnourished individuals, and elderly patients, are at high risk of reactivation or progression of latent TB.
- Immunosuppression weakens the immune system’s ability to keep the pathogen dormant, allowing it to replicate, grow, and spread to other areas, leading to active TB.
14
Q
What are the characteristics of secondary (reactivation) TB, and how does it differ from primary TB?
A
Answer:
- Secondary (reactivation) TB occurs when the latent TB pathogen, previously kept dormant, is reactivated due to a temporary period of immune system depression.
- The bacteria start to multiply and grow, moving upward from the Ghon complex to the upper lobes of the lungs.
- This reactivation causes fibrocaseous necrosis and consolidation in the upper lungs, resulting in fibrocavitary lesions.
15
Q
How can you differentiate between primary TB and reactivation (secondary) TB based on the affected lung lobes?
A
Answer:
- In primary TB, the Ghon complex typically affects the lower and middle lobes of the lungs.
- In contrast, in reactivation (secondary) TB, the infection progresses from the latent phase to the upper lobes of the lungs, resulting in fibrocaseous necrosis and fibrocavitary lesions in the upper lungs.
16
Q
What is primary progressive TB, and what patient populations are at a higher risk for developing this form of TB?
A
Answer:
Primary progressive TB is a form of tuberculosis where the immune system is not strong enough to contain and keep the infection dormant after the initial exposure.
Patients with certain risk factors, such as HIV infection, post-transplant status, immunosuppressive medications, diabetes mellitus, chronic kidney disease, alcoholism, malnourishment, and elderly patients, are at higher risk of developing primary progressive TB.
17
Q
How do primary progressive TB and secondary reactivation TB present clinically, and why do they appear similar?
A
Answer: P
rimary progressive TB and secondary reactivation TB have similar clinical presentations.
- In both cases, the infection progresses to the upper lobes of the lungs, causing fibrocavitary lesions.
The difference lies in the underlying mechanism:
- in primary progressive TB, the immune system is initially unable to contain the infection, whereas in
- secondary reactivation TB, the infection is reactivated due to temporary immune system depression.
18
Q
Which pulmonary complications can occur in patients with TB, particularly in cases of fibrocaseous lesions, consolidations, Ghon complex, and hilar lymphadenopathy?
A
Answer:
Patients with TB, particularly those with fibrocaseous lesions, consolidations, Ghon complex, and hilar lymphadenopathy, can experience the following pulmonary complications:
- Pneumothorax: Fibrocavitary lesions in the upper lobe may extend into the parenchyma and pleura, leading to air leakage into the pleural cavity.
- Bronchopneumonia: Fibrocaseous necrosis may impede the clearance of pathogens, leading to the development of bronchopneumonia.
- Pleural effusion (TB pleurisy): Inflammatory cytokines released from the Ghon complex can cause increased capillary permeability and fluid leakage, leading to pleural effusion.
- Hemoptysis: Fibrocavitary lesions can erode bronchial blood vessels, leading to coughing up blood (hemoptysis).
- Productive cough: Compression of nearby bronchial systems by fibrocavitary lesions can cause inflammation and trigger a productive cough.
- Fever: Cytokines released from granuloma and fibrocaseous necrosis, such as IL-1, IL-6, and TNF-α, affect the hypothalamus, leading to fever, night sweats, and weight loss.
19
Q
How do symptoms differ between primary TB, secondary TB, and asymptomatic cases?
A
Answer:
Often, primary TB patients, and sometimes secondary TB patients, may be asymptomatic. However, when symptoms are present:
- Primary TB: Symptoms may include fever, productive cough, and lymphadenopathy (hilar lymphadenopathy).
- Secondary TB: Symptoms are similar to primary TB, with additional features like hemoptysis due to fibrocavitary lesions.
- Asymptomatic cases: These cases show no noticeable symptoms and are often detected through routine screening or contact tracing.
20
Q
hat are the features of pulmonary tuberculosis, whether it’s secondary reactivation TB or primary progressive TB?
A
Answer:
- hemoptysis,
- productive cough,
- fever,
- night sweats, and
- weight loss.
21
Q
What are the complications associated with tuberculosis?
A
Answer:
pneumothorax,
bronchopneumonia, and
pleural effusion.
22
Q
What clinical signs should you look for when suspecting tuberculosis?
A
Answer:
look for symptoms like hemoptysis, productive cough, fever, night sweats, and weight loss.
23
Q
What is the typical presentation of primary TB?
A
Answer: Often, primary TB is completely asymptomatic, showing no noticeable symptoms.
24
Q
What are the characteristics of extrapulmonary tuberculosis, specifically systemic miliary TB?
A
Answer:
Extrapulmonary tuberculosis, specifically systemic miliary TB, occurs when TB spreads to other organs through the bloodstream, causing disease in multiple areas of the body.
25
What are the signs and symptoms of TB meningitis?
Answer:
headache, focal neural deficits, nausea, vomiting, and photophobia.
26
What is scrofula (cervical lymphadenitis) associated with tuberculosis?
Answer: Scrofula is characterized by swelling of the cervical lymph nodes and is a manifestation of tuberculosis.
27
What is constrictive pericarditis, and how is it related to tuberculosis?
Answer:
Constrictive pericarditis occurs when the pericardium of the heart becomes fibrotic and calcified.
It can be associated with tuberculosis.
28
What are the clinical manifestations of hepatitis caused by tuberculosis?
Answer:
* Hepatitis caused by tuberculosis leads to liver injury and an increase in AST and ALT levels in the blood.
* Symptoms include abdominal pain (right upper quadrant), hepatomegaly, and elevated liver function tests (LFTs).
29
What is sterile pyuria, and how is it related to TB?
Answer:
* Sterile pyuria occurs when TB infiltrates the kidney, causing an increase in white blood cells in the urine.
* TB is not detected in urine cultures in such cases.
30
Which organ does Addison's disease affect, and how is it linked to tuberculosis?
Answer:
* Addison's disease affects the adrenal gland, causing a loss of the ability to produce cortisol and aldosterone.
* It can be associated with tuberculosis.
31
What is Pott's disease, and what symptoms does it present with?
Answer:
Pott's disease is tuberculosis that invades the lumbar vertebrae (L1-L5), leading to severe back pain.
32
Which body part does osteomyelitis related to tuberculosis target?
Answer: Osteomyelitis associated with tuberculosis attacks the long bones.
33
What is the Tuberculin Skin Test (TST), and what is its purpose?
Answer:
* The Tuberculin Skin Test (TST), also known as the Mantoux tuberculin skin test or PPD skin test, is a screening test for tuberculosis (TB).
* It is used to identify individuals at risk of TB, especially those from areas with relevant TB infections, immunocompromised individuals, and those with increased exposure to TB.
34
How is the TST performed, and what does a positive result indicate?
Answer:
* In the TST, tuberculin is injected into the skin, and after 48-72 hours, the healthcare provider checks for an inflammatory or immune response.
* A positive result indicates an immune response, suggesting exposure to TB. **However, the TST cannot differentiate between active or latent TB infection.**
35
How is the swelling measured in the TST, and what does different measurements indicate?
Answer:
* The swelling or induration at the injection site is measured after 48-72 hours. The interpretations are as follows:
* 5+ mm: Positive in individuals with decreased immune function (e.g., HIV/AIDS, immunosuppressed) and close contacts with active TB.
* 10+ mm: Positive in individuals with increased exposure to TB (e.g., prisons, healthcare workers, homeless individuals, IV drug abusers, immigrants).
* 15+ mm: Positive in everyone else.
36
What is the recommended approach when a person has received the BCG vaccine and undergoes a TST?
Answer:
* If a person has received the BCG vaccine, the TST may result in a false positive.
* In such cases, the Interferon-gamma Release Assay (IFGRA) is recommended to differentiate between a BCG-induced response and a true TB infection.
37
What causes a false negative result in the TST?
Answer:
* A false negative result in the TST may occur in individuals with a poor immune response, such as those with HIV infection or sarcoidosis.
* **To confirm the diagnosis, the Interferon-gamma Release Assay (IFGRA) can be performed in such cases.**
38
What radiographic finding suggests primary tuberculosis?
Answer:
* The radiographic finding of a Ghon complex suggests primary tuberculosis.
* It consists of a Ghon focus, which is a granuloma in the lung from a previous TB infection, along with hilar lymphadenopathy.
* Ghon complexes are typically located at the lower or middle lobe of the lung.
39
What is the significance of a Ranke complex in imaging studies?
Answer:
* A Ranke complex is characterized by the fibrocalcification of Ghon foci.
* It indicates a healed primary pulmonary tuberculosis and does not suggest active TB.
40
How does active TB appear on imaging?
Answer:
* Active TB on imaging shows fibro-caseating necrosis with consolidation in the upper lobe areas of the lungs.
* It may present as cavitary opacities, granulomas, and focal consolidations.
41
What does miliary TB look like on imaging, and how does it differ from other forms of TB?
Answer:
* Miliary TB appears as nodular opacities that spread diffusely to the extrapulmonary system.
* It is considered the most severe form of TB due to its widespread dissemination throughout the body.
42
What is the gold standard for diagnosing tuberculosis?
Answer:
* The gold standard for diagnosing tuberculosis is obtaining sputum samples for acid-fast bacillus (AFB) smear and culture.
* Three cultures, taken at least 8 hours apart, are typically required for confirmation.
43
When is bronchoscopy used in the diagnosis of tuberculosis, and what does it reveal?
Answer:
* Bronchoscopy is used to examine the airways and collect samples in patients suspected of having tuberculosis.
* It can reveal caseating granulomas, which are characteristic of tuberculosis.
* During bronchoscopy, a piece of the caseating lesion may be obtained for further analysis.
44
What is the treatment regimen for latent tuberculosis?
Answer:
* The treatment regimen for latent tuberculosis involves either Isoniazid (INH) plus B6 or Rifampin for 3 months.
(INH) plus B6 and Pyridoxine for 6 months
* The combination of INH and B6 is recommended for high-risk patients (e.g., HIV-positive individuals, healthcare workers, prisoners), while Rifampin is an alternative option.
45
What is the recommended treatment regimen for active tuberculosis?
Answer:
* The recommended treatment for active tuberculosis is
the RIPE regimen, which includes Rifampin, Isoniazid (INH), Pyrazinamide, and Ethambutol or
* Pyrazinamide may be substituted with Streptomycin if there is eye disease, as Ethambutol can cause optic neuritis.
46
What adverse drug reactions are associated with the anti-TB drugs?
Answer: Adverse drug reactions of anti-TB drugs include:
* Rifampin: Red/orange urine, CYP450 inducer leading to the decreased efficacy of other drugs, particularly HIV drugs.
* INH: Peripheral neuropathy due to B6 deficiency, hepatotoxicity.
* Pyrazinamide: Gout (increases uric acid levels), hepatotoxicity.
* Ethambutol: Optic neuritis, resulting in color blindness and decreased visual acuity.
* Streptomycin: Nephrotoxicity and ototoxicity.
47
Why is B6 supplementation added to the treatment regimen?
Answer:
* B6 supplementation is added to the treatment regimen to prevent peripheral neuropathy caused by Isoniazid (INH).
* INH can deplete B6 levels, leading to neurological side effects.
48
Why is Directly Observed Therapy (DOT) considered for TB treatment?
Answer:
* Directly Observed Therapy (DOT) is considered for TB treatment due to the prolonged duration of therapy.
* It involves a healthcare provider directly observing the patient taking their medication to ensure compliance and treatment success.
49
What is the main characteristic of tuberculosis (TB) pathology?
Answer:
* Tuberculosis is characterized by delayed (type IV) hypersensitivity, leading to the formation of granulomas with necrosis.
* The T-cell response causes granulomatous inflammation, tissue necrosis, and scarring, which is a hypersensitivity (type IV) reaction.
50
What is Aspergilloma, and how is it related to TB?
Answer:
* Aspergilloma is a condition where the Aspergillus fungus clumps together in a lung cavity.
* **It can occur as a secondary condition to underlying conditions like TB.**
* Patients with Aspergilloma may present with symptoms like haemoptysis, making it an important differential diagnosis in such cases.
51
What are the main causative organisms of tuberculosis in humans?
Answer:
* The main causative organism of tuberculosis in humans is Mycobacterium tuberculosis, which is a rod-shaped gram-positive bacillus.
* It is characterized by acid-fastness due to the waxy coating on its surface, making it resistant to staining procedures like Gram staining.
52
Can M. bovis cause tuberculosis in humans, and how does it happen?
Answer:
* Yes, M. bovis can cause tuberculosis in humans. It is transmitted from cattle to humans, jumping the species barrier.
* Human infection with M. bovis is typically acquired through the consumption of contaminated milk or meat from infected cattle.
53
How does the acid-fastness of Mycobacterium tuberculosis contribute to its resistance to staining procedures?
Answer:
* The acid-fastness of Mycobacterium tuberculosis is due to its waxy coating, which makes traditional Gram staining ineffective.
* This waxy coat resists the acids used in the staining procedure, allowing the TB bacteria to retain the stain and appear red with specialized acid-fast staining methods like the Ziehl-Neelsen stain.
54
What are some risk factors for developing tuberculosis (TB)?
Answer:
* Immigrants
* Recent contacts with active TB cases (higher risk if
exposed within the last 2 years)
* Social deprivation (close contact with infected individuals)
* Immunosuppression (due to conditions like HIV or
* aging, or
* due to immunosuppressive therapies like steroids or chemotherapy)
55
What is Multi-Drug Resistant TB (MDR TB)?
Answer:
refers to strains of tuberculosis that are resistant to more than one TB drug, making them challenging to treat with standard anti-TB medications.
56
What are the main characteristics of primary TB?
Answer: a small focus (Ghon focus) in the periphery of the mid zone of the lung, along with large hilar nodes that appear granulomatous.
57
What are the main characteristics of secondary TB?
Answer:
fibrosing and cavitating apical lesions, which can mimic cancer and are important to differentiate from TB.
58
What is the pathophysiology of tuberculosis?
Answer:
* Tuberculosis is caused by Mycobacterium tuberculosis transmitted via the aerosol route to the alveoli.
* The pathogen is phagocytosed in the alveoli and carried to hilar lymph nodes, leading to a granulomatous immune response with caseous necrosis in the nodes.
* In most cases, the infection becomes latent (LTBI), but in some instances, it can spread throughout the body, leading to extra-pulmonary TB or miliary TB.
* The pathophysiology involves type IV hypersensitivity reactions.
59
Why is it difficult to culture tuberculosis (TB)?
Answer:
* TB bacteria are slow-dividing with high oxygen demands, making them difficult to culture in laboratory settings.
* Their slow growth rate requires specialized culture media and extended incubation periods.
60
What is an Active TB infection?
Answer:
* Active TB infection refers to the presence of actively replicating Mycobacterium tuberculosis bacteria in various areas of the body.
* In most cases, the immune system is able to control and clear the infection, preventing it from progressing further.
61
What is latent TB?
Answer:
* Latent TB occurs when the immune system successfully encapsulates sites of TB infection, stopping the progression of the disease.
* In this state, the TB bacteria remain dormant and do not cause active symptoms or spread to other areas.
62
What is secondary TB?
Answer:
* Secondary TB occurs when latent TB reactivates, leading to active infection and disease.
* This can happen when the immune system becomes compromised or weakened, allowing the dormant bacteria to start replicating again.
63
What is miliary TB?
Answer:
* Miliary TB is a severe form of TB where the immune system is unable to control the infection, leading to disseminated disease.
* In miliary TB, numerous tiny foci of infection (like millet seeds) spread throughout the body via the bloodstream, affecting various organs.
64
Why is the lung the common site for TB?
Answer:
* The lung is a common site for TB infection because it is where the TB bacteria are inhaled into the alveoli.
* The oxygen-rich environment in the lungs supports the growth of TB bacteria, leading to primary TB infection in this area.
65
Why does tuberculosis affect apices of the lungs?
Answer:
* Tuberculosis affects the apices of the lungs due to the relatively higher oxygen tension in these areas.
* Additionally, delayed lymphatic drainage in the apical regions allows the TB bacteria to persist and lead to the formation of granulomas and caseous necrosis.
66
What is Extrapulmonary TB?
Answer:
Extrapulmonary TB refers to tuberculosis infections that occur outside the lungs.
* It can affect various areas of the body, including lymph nodes, pleura, central nervous system, pericardium, gastrointestinal system, genitourinary system, bones and joints, and even the skin (cutaneous TB).
67
What percentage of TB cases present with pulmonary features only?
Answer: Approximately 90% of TB cases present with pulmonary features only, primarily manifesting as cough and, in some cases, hemoptysis (coughing up blood).
68
What is Pott's disease of the spine?
Answer: Pott's disease is another term for spinal TB. It presents with spinal pain and is a form of extrapulmonary TB that affects the vertebral bones.
69
What is the common sequence of symptoms in pulmonary TB?
Answer: In pulmonary TB, the common sequence of symptoms is a continuous cough followed by the occurrence of hemoptysis (coughing up blood).
70
Which symptom is commonly associated with TB?
Answer: Night sweats are commonly associated with TB and can be a key indicator of the disease.
71
What is the gold standard test for diagnosing TB?
Answer: The gold standard test for diagnosing TB is the sputum acid-fast bacilli (AFB) smear. It involves staining sputum samples to detect the presence of acid-fast bacteria, specifically Mycobacterium tuberculosis.
72
What is the purpose of the Mantoux test?
Answer:
* The Mantoux test, also known as the tuberculin skin test (TST), is used to assess possible previous vaccination, latent TB, or active TB.
* However, it cannot distinguish between latent and active TB.
73
Is the BCG vaccine effective against pulmonary TB?
Answer: No, the BCG vaccine is less effective against pulmonary TB. It provides some protection against severe forms of TB in children but does not reliably prevent pulmonary TB.
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