Tuberculosis natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mashal Awais, M.D.[2];Sophia Saad, Associate Editor - WikiDoc [3] João André Alves Silva, M.D. [4] Template:Tuberculosis Natural History, complications, and prognosis

Tuberculosis natural history, complications, and prognosis

Natural history

Latent tuberculosis infection (LTBI)

In the absence of treatment, approximately 5% to 15% of immunocompetent persons with LTBI progress to active TB disease over a lifetime, with estimates varying by source (ATS/IDSA/CDC diagnostic guideline estimates 4%–6%; USPSTF cites 5%–10%; NEJM review cites 5%–15%).

People with untreated HIV infection have an estimated annual risk of progression to TB disease of 3% to 16%.

Untreated active tuberculosis

Untreated active TB can progress over weeks to months with ongoing tissue destruction and increased transmission risk (for pulmonary disease). Pre-chemotherapy era systematic reviews provide the following estimates for HIV-negative individuals: untreated smear-positive pulmonary TB has a 10-year case fatality of approximately 70% (weighted mean), while culture-positive, smear-negative TB has an estimated 10-year case fatality of approximately 20%.

The average duration of untreated pulmonary TB from onset to cure or death is approximately 3 years, though Bayesian re-analysis estimates shorter duration for smear-positive disease (~1.6 years) and longer for smear-negative disease (~5.4 years). Natural recovery occurs in a substantial minority of untreated smear-positive cases.

In children (pre-treatment era), case fatality was 44% in those aged 0–4 years and 15% in those aged 5–14 years.

Complications

Pulmonary complications

Common pulmonary complications include:

• Cavitation
• Hemoptysis (including massive hemoptysis; e.g., Rasmussen's aneurysm)
• Pneumothorax
• Empyema
• Bronchiectasis / post-infectious airway disease
• Acute respiratory distress syndrome (ARDS) (uncommon; more likely with severe disseminated disease)

Extrapulmonary and disseminated complications

Miliary tuberculosis and other disseminated forms (hematogenous spread).

Site-specific complications may include neurologic disability from tuberculous meningitis, pericardial complications (effusion/constriction), skeletal deformity from spinal TB, and infertility/obstructive uropathy from genitourinary TB.

Post-tuberculosis sequelae (after microbiologic cure)

Risk factors associated with post-TB sequelae have been summarized in systematic review and meta-analysis.

Quantitative estimates of post-TB lung disease (PTLD) burden include: approximately 50% of pulmonary TB survivors have abnormal spirometry at or after treatment completion, with severe impairment in 10%–15%; bronchiectasis is observed in 35%–86% on imaging.

Chronic pulmonary aspergillosis (CPA) prevalence in TB survivors ranges from 7% to 23%, with residual cavitation being the strongest risk factor (annual incidence of new CPA ~6.5% in those with cavitation vs 0.2% without).

TB survivors have an estimated standardized mortality ratio of approximately 2.9 compared with the general population, with cardiovascular disease, cancer, and respiratory diseases among the leading causes of post-treatment death. Among post-treatment deaths, approximately 20% are attributable to cardiovascular disease. Post-TB excess mortality is highest in the first year after diagnosis (mortality rate ratio ~11) and declines progressively, reaching ~1.5 by year 10, but remains elevated for at least 14 years.

People with prior TB have an approximately 1.6-fold increased risk of all cancers and a 3.2-fold increased risk of lung cancer compared with controls.

Long-term sequelae after pulmonary TB (including cardiopulmonary impairment and chronic respiratory symptoms) are reviewed in narrative and European Respiratory Society publications.

Prognosis

Prognosis by drug susceptibility pattern

Mortality differs substantially by drug susceptibility pattern in treated TB cohorts from high-burden countries.

Drug susceptibility pattern	Reported mortality (treated cohort)	Clinical notes
Pan-susceptible TB	6%	Observational multicentre cohort; mortality varies by setting and comorbidity burden.
Isoniazid-monoresistant TB	30% (7/23 patients)	Small subgroup treated with first-line regimens; a larger meta-analysis (25 studies) found pooled mortality of 6% overall. Current ATS/CDC/ERS/IDSA guidelines recommend fluoroquinolone-containing regimens, which substantially improve outcomes.
Pre-XDR/XDR TB	35%	High mortality despite treatment; emphasizes prognostic impact of resistance and the importance of effective regimens guided by DST.

Prognosis in HIV co-infection

TB in people with HIV has higher risk of disseminated and extrapulmonary disease and higher mortality, especially with advanced immunosuppression. The CD4+ T-lymphocyte count is the strongest predictor of TB-related mortality in people with HIV. Mortality with treatment is approximately 2.5% for HIV-negative individuals and approximately 14% for people with HIV.

Initiation of antiretroviral therapy (ART) during TB treatment reduces mortality by approximately 24% overall and reduces HIV disease progression by 34%.

Immune reconstitution inflammatory syndrome (IRIS) is a clinically important complication after ART initiation in TB-HIV co-infection; paradoxical TB-IRIS occurs in approximately 18% of patients starting ART.

Prognosis of TB meningitis

TB meningitis carries the highest mortality of any TB form, with case fatality rates of approximately 20–30% in HIV-negative patients and up to 50% in HIV-positive patients, even with treatment. Mortality is strongly associated with MRC stage at presentation: stage I has the best prognosis, while stage III (GCS ≤10) carries the highest mortality. Survivors frequently have permanent neurologic sequelae.