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Questions and Answers
What is tuberculosis (TB)?
What is tuberculosis (TB)?
Tuberculosis is a chronic specific systemic infectious disease caused by bacteria called Mycobacterium tuberculosis.
Which bacterium is the causative organism of tuberculosis?
Which bacterium is the causative organism of tuberculosis?
What is the most common route of infection for tuberculosis?
What is the most common route of infection for tuberculosis?
Which of the following is NOT a risk factor for tuberculosis?
Which of the following is NOT a risk factor for tuberculosis?
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What type of necrosis is detected in tuberculosis?
What type of necrosis is detected in tuberculosis?
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Epithelioid cells are modified:
Epithelioid cells are modified:
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The organs where TB granulomas commonly form include the lungs, tonsils, and _____
The organs where TB granulomas commonly form include the lungs, tonsils, and _____
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What are the two types of TB infections?
What are the two types of TB infections?
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What are some common clinical presentations of tuberculosis?
What are some common clinical presentations of tuberculosis?
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Study Notes
Tuberculosis (TB)
- A chronic, infectious disease caused by the bacteria Mycobacterium tuberculosis.
- Characterized by the formation of caseous epithelioid cell granulomas in various organs.
Etiology
- Caused by Mycobacterium tuberculosis (human and bovine strains).
- The bacteria are identified using the Ziehl-Nielson Stain.
Infection Sources
- Humans or animals
- Routes of infection:
- Inhalation of infected droplets: Most common route, infecting the lungs or tonsils.
- Ingestion of infected milk: Infects the tonsils or intestines
- Inoculation through skin: Contact with infected materials.
Risk Factors
- Diabetes mellitus
- Malignant tumors
- Chronic lung disease
- Chronic renal failure
- Malnutrition
- Alcoholism
- Immune suppression (e.g., AIDS).
- TB thrives in environments with poverty, crowding, and chronic illness.
Clinical Presentation
- Coughing up blood or mucus
- Night sweats
- Weight loss
- Tiredness
- Chest pain
- Pain during breathing or coughing
- Fever (especially at night)
Body Reaction to TB
-
Proliferative (cellular) tissue reaction:
- Common in primary TB.
- Results in the formation of TB granulomas in solid organs.
- TB granulomas contain:
- Epithelioid cells (modified macrophages)
- Langhans' giant cells (fused epithelioid cells)
- Lymphocytes
- Fibroblasts
- Caseation necrosis (a type of cell death)
-
Exudative tissue reaction:
- Occurs in secondary TB.
- Usually occurs in serous membranes.
- Involves the accumulation of inflammatory fluid rich in lymphocytes and fibrin.
Types of TB Infection
-
Primary Infection:
- Leads to primary TB disease.
-
Secondary Infection:
- Leads to secondary TB disease.
Primary Tuberculosis
- Occurs in previously unexposed individuals (non-immunized).
- Often seen in children.
- Characterized by the primary complex, with minimal tissue destruction.
- Sites of infection:
- Lungs
- Tonsils
- Small intestine
- Skin
- Outcome depends on the number of bacilli and the patient's immunity:
- Complete healing (most common)
- Incomplete healing
- Progression and complications (rare)
Secondary TB
- Occurs in previously infected individuals.
- Typically seen in adults.
- Reactivation or reinfection.
- Significant tissue destruction with:
- Large granulomas
- Caseation necrosis
- Cavity formation
- Can be pulmonary OR extrapulmonary.
- Outcome:
- Local or systemic spread
- Miliary TB (disseminated TB)
Fate of Tuberculosis
- Good body resistance: Healing by fibrosis.
-
Poor body resistance: Spread of infection:
- Direct: To adjacent tissues, forming new lesions.
- Lymphatic: To regional lymph nodes.
- Blood: Generalized miliary TB (spread of bacteria throughout the body) or isolated organ TB.
- Serous cavities: Along pleura, peritoneum, etc.
- Natural passages.
Pulmonary TB
-
Primary Pulmonary TB:
- Consists of:
- Ghon's focus: primary lesion in the lung.
- Lymphangitis: Inflammation of lymph vessels.
- Lymphadenitis: Inflammation of lymph nodes.
- Consists of:
-
Secondary Pulmonary TB:
- Endogenous source: Reactivation of a dormant primary complex.
- Exogenous source: New infection.
- Lesions:
- Apical cavitation: Cavities at the top of the lung.
- Multiple small caseous foci: Small areas of caseation necrosis in the base of the lung.
- Tuberculous bronchopneumonia: Inflammation of the bronchioles and alveoli.
Intestinal TB
-
Primary TB:
- Primary complex and tuberculous lymphadenitis.
-
Secondary TB:
- Tuberculous ulcer in the small intestine (Girdle Ulcer).
-
Hypertrophic Ileocecal TB:
- Large, hard mass in the right iliac fossa.
- TB Peritonitis: Inflammation of the peritoneum.
Bone TB
- Vertebrae: Pott's disease (TB of the spine).
- Long Bones: TB osteomyelitis (TB infection of the bone).
- Short Bones.
- Joints: TB arthritis.
Genitourinary TB
- TB pyelonephritis: TB infection of the kidney.
- TB salpingitis: TB infection of the fallopian tubes.
- TB epididymitis: TB infection of the epididymis.
-
Complications:
- Obstructive infertility in males and females.
- Renal failure (uraemia).
Central Nervous System TB
- TB Meningitis: Inflammation of the meninges (membranes surrounding the brain and spinal cord).
- Tuberculoma: A mass of TB cells in the cerebellum or brain stem.
MCQs
-
1. Which type of necrosis is detected in tuberculosis?
- d. Caseation necrosis.
-
2. Epithelioid cells are modified:
- a. Macrophages.
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