TB meets COPD: An emerging global co-morbidity in human lung disease.

Chronic obstructive pulmonary disease (COPD) is emerging as the third largest cause of human mortality worldwide after heart disease and stroke. There is growing evidence of a co-morbidity between COPD and tuberculosis (TB), the leading cause of death globally due to respiratory infection. Thus, the increase in the burden of COPD over the coming decades, as predicted by the World Health Organisation, is of concern with respect to the control of TB. A better understanding of the interactions between these two diseases is essential for the design of complementary preventive and control strategies. In this review, some of the known risk factors that are common to both diseases are discussed. Furthermore, we examine how impairment of the innate immune system, and corticosteroid therapy, in COPD patients may increase the risk of TB manifestation. Conversely, we review how TB lung pathology may heighten susceptibility to subsequent development of COPD, even after completion of effective TB treatment. Growing evidence appears to point towards a bi-directional relationship between these two lung diseases where each may act as an independent risk factor for the other. This has important implications for the respective long-term management of TB and COPD.