Clinical features and complications of tuberculosis spm
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I now have enough comprehensive material from Park's (SPM) and Rosen's Emergency Medicine. Let me compile the full, detailed answer.
Tuberculosis: Clinical Features and Complications (SPM)
Sources: Park's Textbook of Preventive and Social Medicine; Rosen's Emergency Medicine (8th Ed.)
1. Introduction
Tuberculosis (TB) is a specific infectious disease caused by Mycobacterium tuberculosis. It primarily affects the lungs (pulmonary TB) but can involve the intestine, meninges, bones, joints, lymph glands, skin, and other tissues. The disease is usually chronic with varying clinical manifestations.
- About one-third of the world's population is asymptomatically infected
- Only 5-10% will develop clinical disease during their lifetime
- An infectious PTB patient can infect 10-15 persons per year
2. Classification of Tuberculosis
By Anatomical Site:
| Type | Description |
|---|---|
| Pulmonary TB (PTB) | Involves lung parenchyma or tracheobronchial tree. Miliary TB is also classified as PTB |
| Extrapulmonary TB (EPTB) | Involves organs other than lungs: pleura, lymph nodes, abdomen, genitourinary tract, skin, joints, bones, meninges |
By Bacteriological Status:
- Bacteriologically confirmed: Positive smear, culture, or Xpert MTB/RIF (WRD)
- Clinically diagnosed: Diagnosed by clinician based on X-ray, histology, clinical features - without lab confirmation
3. Natural History and Pathogenesis
Incubation Period: Tuberculin test turns positive 3-6 weeks after infection; disease may develop over weeks, months, or even years.
Four Stages of Pathogenesis (Rosen's):
| Stage | Description |
|---|---|
| Stage 1 | Alveolar macrophage phagocytoses the bacillus. A resistant host destroys a less virulent bacillus - no infection develops |
| Stage 2 | Bacilli replicate, macrophage lyses; monocytes attracted and differentiate; bacilli multiply logarithmically within macrophages, spread via lymphatics to lymph nodes, kidneys, epiphyses of long bones, vertebral bodies, meningeal areas, and apical lung zones |
| Stage 3 | 2-3 weeks after infection: cell-mediated immunity kicks in via CD4+ T-cells. Cytokines activate macrophages to kill bacilli. Primary lesion walled off. In immunocompetent: 8-10% develop active TB; in HIV-infected: 37% within 6 months progress to active TB |
| Stage 4 | Months to decades later - reactivation of dormant foci due to decreased host resistance. This is "postprimary TB." The primary walled-off tubercle erodes through bronchial wall, forms a cavity |
4. Clinical Features
A. Presumptive Case (WHO Definition)
A patient who presents with symptoms or signs suggestive of TB (previously called a "TB suspect").
B. Symptoms of Pulmonary TB
Respiratory (Local) Symptoms:
- Persistent cough (most common - present in majority; >60% of patients seek medical advice because of this)
- Haemoptysis - minor to major (including massive, fatal haemoptysis from Rasmussen aneurysm)
- Chest pain / pleuritic pain
- Dyspnoea (in advanced disease)
Constitutional (Systemic) Symptoms:
- Fever - characteristically low-grade, evening rise ("afternoon fever")
- Night sweats
- Weight loss / anorexia
- Fatigue / malaise
- Loss of appetite
Park's notes: "An overwhelming majority of patients of pulmonary TB have one or more symptoms referable to chest, such as persistent cough and fever, and many of them (over 60%) seek medical advice on their own initiative."
C. Signs
- Low-grade fever
- Weight loss / cachexia
- Clubbing (in chronic disease)
- Reduced air entry, dullness to percussion in affected zones (usually upper lobes/apical)
- Bronchial breath sounds
- Post-tussive crepitations
- Evidence of cavity formation
D. Chest X-Ray Findings
- Upper lobe infiltrates (apical/posterior segments of upper lobes - preferred areas due to higher O₂ tension)
- Cavitation
- Nodular/patchy opacities
- Pleural effusion
- Hilar lymphadenopathy
- Miliary pattern (miliary TB)
- Calcified Ghon focus (primary complex healed)
5. Primary vs. Post-Primary (Reactivation) TB
| Feature | Primary TB | Post-Primary (Reactivation) TB |
|---|---|---|
| Age | Usually children | Adults |
| Location | Any lobe; mid/lower zones | Upper lobe - apical/posterior |
| Ghon focus | Present | Absent |
| Lymph node involvement | Prominent | Less common |
| Cavitation | Uncommon | Common |
| Spread | Lymphohematogenous (miliary) | Local bronchogenic |
6. Special Forms
Miliary TB
- Haematogenous dissemination - millet seed-like lesions throughout both lungs and other organs
- Features: high fever, toxaemia, dyspnoea, weight loss
- More common in very young children and immunocompromised patients
- CXR: diffuse bilateral millet-seed (1-2 mm) nodular shadows
Childhood TB (Park's emphasis)
- 6-8% of all TB cases are in children under 15 years
- Source: usually an adult family member with sputum smear-positive TB
- Under 5 years: up to 20% develop disease within 2 years of infection
- Commonest age: 1-4 years
- Children rarely have smear-positive TB and are not efficient transmitters
- Young age is a risk factor for dissemination (miliary/meningeal TB)
7. Complications of Tuberculosis
A. Pulmonary Complications
| Complication | Details |
|---|---|
| Haemoptysis | Minor (very common from vessel rupture in parenchymal destruction) to massive (from Rasmussen aneurysm - erosion of pulmonary artery by tuberculous cavity). May require emergency surgical resection or selective embolization |
| Spontaneous Pneumothorax | <5% of patients with severe cavitary disease. Occurs when a cavity ruptures creating a bronchopleural fistula, or when a bleb ruptures into pleural space. Delayed treatment leads to progressive fibrosis and air trapping |
| Pleural Effusion | Early post-primary infection or late in cavitary disease. Usually exudate; protein >50% of serum protein. 65% relapse rate if untreated (within 5 years), progressing to active PTB or EPTB. AFB smear rarely positive; culture positive in only 25-30% |
| Empyema | Extensive cavitary disease + pleural rupture. Rare but catastrophic. Often associated with bronchopleural fistula. Can cause pleuro-cutaneous fistula, chest wall mass, rib/vertebral destruction |
| Bronchiectasis | Common complication of endobronchial TB; leads to chronic productive cough |
| Bronchial Stenosis | From endobronchial TB or lymphatic spread; causes lobar collapse, hyperinflation, or obstructive pneumonia |
| Laryngeal TB | Most infectious form; proximal extension of lower airway disease. Usually co-exists with active pulmonary disease |
| Aspergilloma (Fungal Ball) | Superinfection of healed open cavities with Aspergillus fumigatus. Can cause massive, fatal haemoptysis |
B. Extrapulmonary / Systemic Complications
| Complication | Details |
|---|---|
| Tuberculous Meningitis | Haematogenous spread; headache, meningism, cranial nerve palsies, altered consciousness; high mortality and morbidity |
| Tuberculous Pericarditis | Direct extension from mediastinal/hilar nodes, sternum, or spine, or haematogenous spread. Leading cause of pericarditis in HIV-positive patients. Features: cough, chest pain, dyspnoea, cardiomegaly, friction rub, fever, tachycardia. Complications: pericardial effusion, constrictive pericarditis, myocarditis, cardiac tamponade |
| Skeletal TB (Pott's Disease) | Vertebral body involvement; risk of spinal cord compression, kyphosis, paraplegia |
| Genitourinary TB | Chronic pyuria with sterile urine ("sterile pyuria"); dysuria, haematuria; strictures |
| Intestinal TB | Ileocaecal region most common; ulceration, stricture, obstruction, perforation |
| Lymphadenitis | Most common form of EPTB; cervical nodes ("scrofula") most common; nodes may become fluctuant and discharge |
| Miliary TB | Haematogenous dissemination to all organs; hepatosplenomegaly, choroidal tubercles in eyes |
| Adrenal TB | Can cause Addison's disease (adrenocortical insufficiency) |
C. Complications Specific to HIV Co-infection
- Faster progression (37% within 6 months vs. 8-10% lifetime risk in immunocompetent)
- Atypical presentations (lower lobe infiltrates, no cavitation)
- Higher risk of disseminated/extrapulmonary TB
- Immune Reconstitution Inflammatory Syndrome (IRIS) on starting ART
- TB is the leading infectious cause of death in HIV-positive patients
8. TB and Comorbidities (SPM Perspective)
- TB + Diabetes Mellitus: Diabetes increases risk of TB 3-fold; TB destabilises glycaemic control; bidirectional relationship
- TB + HIV: HIV is the most powerful risk factor for activating latent TB infection; co-infected patients have higher mortality
- TB + COVID-19: Both cause respiratory disease; COVID-19 may worsen outcomes in TB patients and disrupt TB services
- TB in Pregnancy: Risk of prematurity, low birth weight, congenital TB; treatment must be given (most first-line drugs are safe)
9. Key Epidemiological Points (Park's)
- Communicability: Patients are infective as long as untreated. Effective anti-microbial treatment reduces infectivity by 90% within 48 hours
- Sex: More prevalent in males than females
- Age in India: Infection rate ~2% in 0-14 yrs age group, climbs to ~20% at 15-24 yrs
- TB is NOT transmitted by fomites (dishes, clothes)
- Patients with extrapulmonary or smear-negative TB constitute a minimal hazard for transmission
10. Summary Mnemonic for Clinical Features
"FLAWS WC" - common symptoms:
- Fever (low-grade, evening rise)
- Loss of weight and appetite
- Anorexia / fatigue
- Weight loss
- Sweats (night sweats)
- Weakness / malaise
- Cough (persistent) + haemoptysis
Park's Textbook of Preventive and Social Medicine, pp. 211-220 (Community Medicine/SPM)
Rosen's Emergency Medicine: Concepts and Clinical Practice, pp. 2707-2712 (Complications of Pulmonic Tuberculosis)
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