By Dr Ananya Mandal, MD
Tuberculosis is a curable disease. Progress of tuberculosis from infection to frank illness involves overcoming of the immune system defences by the bacteria. As the bacteria start to multiply, it affects the immune system and finally overwhelms it to cause the disease.
Once diagnosed, with effective, adequate and appropriate therapy with anti tubercular drugs, treatment is possible and so is cure.
In primary tuberculosis, that forms around 1 to 5% of all cases, the progression of the infection to frank disease occurs soon after infection. In many, the initial infection is latent tuberculosis. The disease may remain dormant within the body with the immune system capable of containing the infection.
When the immune system weakens for some reason (e.g. HIV infection, diabetes, renal disease etc.) there is reactivation of the infection. The risk of this reactivation rises when immunity is suppressed. For example, those with concomitant HIV infection have an increased risk of reactivation of tuberculosis of 10% each year of infection.
Tuberculosis concomitant with HIV infection
Tuberculosis concomitant with HIV infections is on the rise and this makes detection and treatment a challenge. In addition, the rise of drug-resistant strains of tuberculosis have contributed to the epidemic and there are 20% of cases of tuberculosis which are caused by strains of tuberculosis that are resistant to standard treatments and 2% of the strains are resistant to second-line drugs.
Predictors of poor prognosis
Some predictors of a poorer prognosis include extreme ages and other medical conditions. In Africa, tuberculosis mainly affects young adults and teenagers. In some developed countries, however, tuberculosis mainly affects the elderly.
Other risk factors that increase the risk of poor prognosis include smoking more than 20 cigarettes a day that raises risk of tuberculosis itself by two to four times. Diabetes also worsens the prognosis and outcome of tuberculosis.
Other disease states that raise risk of tuberculosis and worsen prognosis include:
end-stage renal disease
chronic lung disease
Those with iron, vitamin B12 or vitamin D deficiency are also at risk.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Jan 29, 2013