Recent developments in the diagnosis and treatment of extrapulmonary non-tuberculous mycobacterial diseases

Diseases due to pathogenic mycobacteria cause significant health and economic impact on humans worldwide. Although mycobacterial diseases primarily affect the lungs, the involvement of extrapulmonary organs has also gained ground, particularly among individuals with co-existing medical conditions. Besides Mycobacterium tuberculosis complex organisms, non-tuberculous mycobacteria (NTM) are also known to cause pulmonary and extrapulmonary diseases. Primary and disseminated extrapulmonary mycobacterial infections affect the brain, eye, mouth, tongue, lymph nodes of the neck, spine, bones, muscles, skin, pleura, pericardium, gastro-intestinal, peritoneum and genito-urinary system. The clinical presentation of extrapulmonary mycobacterial diseases, including systemic symptoms, of M. tuberculosis-infected cases and NTM-infected cases is similar. Moreover, extrapulmonary mycobacterial diseases are complicated by the involvement of diverse bacterial species as aetiological agents. Culture and molecular techniques are used to differentiate NTM from Mycobacterium tuberculosis and to classify sub-species of the pathogens. As sub-speciation and drug susceptibility profiling are critical factors in treating extrapulmonary NTM diseases, there are often significant delays in initiating treatment and customising the therapeutic regimen. Here, we summarise the clinical symptoms of NTM diseases in various extrapulmonary organs, and discuss the recent trends in diagnosing and treating these diseases. We also highlight the complications associated with the management of extrapulmonary NTM disease.