The Lancet Respiratory Medicine Journal has published a review by Dr. Elisa López-Varela and Dr. Alberto García Basteiro from ISGlobal, in collaboration with other researchers, in which they summarise the current knowledge on infections by non-tuberculous mycobacteria and discuss how these infections can affect diagnosis and treatment of tuberculosis, especially among children. The authors analyse the implications of this type of infections for public health in countries with a high endemic burden of childhood tuberculosis.    

The Mycobacterium genus is composed of three groups: Mycobacterium tuberculosis (that causes tuberculosis), Mycobacterium leprae (that causes leprosy) and a large family of non-tuberculous mycobacteria (NTM) that are common in water and soil. The latter normally do not cause disease in individuals with a healthy immune system. However, in children, they can occasionally cause lymphadenitis, skin infections, lung disease and even disseminated infections (in patients with genetic or acquired immunodeficiencies, leukemias or solid tumors). As the authors point out, the problem is that these MNT-caused infections cannot be readily distinguished from tuberculosis. Even diagnosis tests such as microscopic smear examination or the tuberculin skin test cannot distinguish between M. tuberculosis and MNT. As Dr. López-Varela explains, "this problem is particularly relevant in settings with high prevalence of tuberculosis, and hinders not only the diagnosis but also the treatment of the disease, since tuberculosis and MNT are not treated in the same way". 

Following an exhaustive review of the available literature on epidemiology, transmission, immune response, symptoms, diagnosis and treatment of MNT infections, the authors identify several research gaps that need to be addressed. For example, the real burden of MNT infections among children in developing countries is not known, and neither are the geographical distribution of NTM species and the transmission mechanisms.  The effect of NTM exposure on the efficacy of existing or novel tuberculosis vaccines is another important issue that remains to be determined. "There is scarce information on the subject and this is the first review on NTM in children" Dr. López Varela points out.  The authors conclude that important efforts are required to develop NMT-specific diagnosis tests and treatments that are adequate for children and applicable in low-resource, tuberculosis-endemic countries.