Nontuberculous mycobacterial lung disease

Abstract

There is increasing awareness that nontuberculous mycobacteria (NTM) lung diseases are becoming more prevalent. Nontuberculous mycobacterial diseases could legitimately be seen as an emerging public-health threat. Nontuberculous mycobacterial lung disease associated radiographically with nodules and bronchiectasis occurs primarily in women. These patients are associated with a specific morphotype, including low BMI, tall stature, scoliosis, pectus excavatum and mitral valve prolapse. The pathophysiologic link between these findings and the development of bronchiectasis and NTM disease remains unclear. As with tuberculosis, the tumor-necrosis factor alpha (TNF-alpha) blockers also predispose to NTM infection that can be severe. The most frustrating aspect of NTM therapy remains the generally poor correlation between in-vitro antibiotic susceptibility and in-vivo response to antimicrobials. A possible insight into this phenomenon is the recent discovery of an inducible macrolide resistance (erm) gene in Mycobacterium fortuitum and Mycobacterium abscessus. This gene can produce in-vivo resistance without resulting in a 'resistant' MIC for macrolides. The NTM pose an increasing problem for clinicians and are associated with significant obstacles that thwart successful treatment of NTM disease. Continued progress in the areas of disease pathogenesis and therapy will improve the outlook for these patients.