Clinical manifestations and consequences
While any organ of the human body can be affected by TB, in HIV-negative individuals pulmonary disease is the most frequent clinical manifestation (70–80% of cases). Extrapulmonary involvement (for instance, meningitis or lymphadenitis) occurs in 20–30% of patients, sometimes accompanied by pulmonary disease; in settings with high HIV prevalence, this proportion can be higher.
Pulmonary and/or extrapulmonary TB can occur many years after exposure to an individual with infectious TB, provoked by temporary or permanent immunological impairment; only on rare occasions do symptoms develop after primary infection.
The most frequent symptoms of active disease are fever, anorexia or reduced appetite, weight loss, night sweats and persistent cough ( i.e . lasting more than 21 days), usually productive of purulent and/or blood-stained sputum. Occasionally, patients complain of localised thoracic pain due to pleural inflammation; in extensive and long-lasting pulmonary disease, patients may complain of breathlessness (dyspnoea) and of coughing up blood (haemoptysis).