27th June 2023

Reactivation tuberculosis

HIV-associated immunosuppression accelerates tuberculosis progression, either via primary infection or reactivation of latent infection, and TB accelerates CD4+ T cell loss, thereby accelerating HIV, i.e. TB and HIV both increase the rate of progression of the other disease. Patients started on antiretroviral therapy after AIDS may develop immune reconstitution inflammatory syndrome (IRIS), which is worse with TB. Immune reconstitution causes inflammation, with recurrence of TB symptoms, abscess formation and lymphadenopathy. Neurological involvement can lead to death. Clinical presentations in pulmonary TB may include haemoptysis and features of pneumonia.

More immunocompromised patients will often have less typical features of pulmonary TB:

• Lower lobe involvement
• Tuberculous pneumonia
• Miliary TB
• Hilar/ mediastinal lymphadenopathy

TB in HIV has lower bacillary loads in sputum, meaning traditional staining is infrequently positive. Tuberculin skin testing is less frequently positive in patients with lower CD4+ T-cell counts, which requires a functional Th1 cytokine response. Broncho-alveolar lavage or bronchial biopsy may therefore be needed. Cavitation is less likely, with more isolated extrapulmonary disease. TB treatment in HIV is the same as if seronegative-rifampicin, isoniazid, pyrazinamide, and ethambutol are given for two months, followed by four months of rifampicin and isoniazid. HIV infection increases the risk of adverse events associated with anti-tuberculosis medications, including:

• Skin reactions
• Drug-induced liver injury
• Peripheral neuropathy with isoniazid (pyridoxine prophylaxis is given)
• Drug interactions with antiretroviral therapy

Rifampicin strongly induces cytochrome P450 3A4, therefore, rifabutin is recommended instead in patients taking non-nucleoside reverse transcriptase inhibitors or protease inhibitors. In treatment-naïve patients, the priority is the treatment of TB before highly active antiretroviral therapy (HAART) is initiated.