18. Pulmonary TB: clinical symptoms, diagnosis, treatment

Pulmonary tuberculosis: clinical symptoms, diagnosis and treatment

AETIOLOGY & PATHOGENESIS

• Pulmonary tuberculosis (TB) is caused mainly by Mycobacterium tuberculosis and spreads through airborne droplet nuclei from a person with infectious pulmonary or laryngeal disease.
• Inhaled bacilli reach alveoli and are taken up by macrophages. Cell-mediated immunity produces granulomas, often with caseous necrosis. Infection may be latent or progress to active disease.
• Primary TB may produce a parenchymal focus and hilar lymphadenopathy. Reactivation commonly affects upper lobes where oxygen tension is high and may cause cavitation and bronchogenic spread.
• Risk factors for progression include HIV, immunosuppression, diabetes, malnutrition, renal failure, silicosis, young age and recent infection.

CLINICAL FEATURES

• Constitutional symptoms include prolonged fever, night sweats, weight loss, anorexia and fatigue.
• Respiratory symptoms include cough lasting weeks, sputum production, haemoptysis, chest pain and dyspnoea.
• Examination may be normal or show crackles, bronchial breathing, signs of consolidation, cavitation or pleural effusion. Extrapulmonary symptoms suggest disease elsewhere.

DIAGNOSIS

• Obtain sputum for rapid molecular testing (e.g. Xpert MTB/RIF or equivalent), smear microscopy and mycobacterial culture with drug-susceptibility testing.
• Chest radiograph may show upper-lobe infiltrates, cavities, nodules, miliary pattern, lymphadenopathy or pleural effusion. CT is useful for complex or uncertain cases.
• A positive tuberculin skin test or interferon-gamma release assay indicates TB infection but cannot distinguish latent infection from active disease.
• Assess HIV status and relevant comorbidities. Bronchoscopy or induced sputum may be needed if sputum cannot be obtained and suspicion remains high.
• Differentiate from bacterial pneumonia, lung cancer, fungal infection, nontuberculous mycobacteria, sarcoidosis and bronchiectasis.

TREATMENT & INFECTION CONTROL

• Notify public health authorities and institute airborne infection precautions for suspected infectious pulmonary TB according to local policy.
• Drug-susceptible pulmonary TB is generally treated with an initial multidrug phase using isoniazid, rifampicin, pyrazinamide and ethambutol, followed by isoniazid and rifampicin; exact duration and regimen depend on current national guidance and susceptibility.
• Add pyridoxine with isoniazid in patients at risk of neuropathy. Monitor liver toxicity, visual symptoms with ethambutol, drug interactions and adherence.
• Drug-resistant TB requires specialist-directed regimens based on susceptibility testing. Directly observed or supported treatment and contact tracing improve completion and reduce transmission.
• Surgery is rarely required; indications may include localised destroyed lung, major haemoptysis, persistent cavity or diagnostic uncertainty after medical therapy.
• Complications include haemoptysis, bronchiectasis, fibrosis, respiratory failure, pleural disease, dissemination and drug toxicity. Follow clinical response, sputum conversion and imaging.