The mycobacterial mystery.

B efore the advent of HIV, which led to an increased awareness of Mycobacterium avium complex disease, followed by the first prospective comparison studies on treatment regimens [1, 2], the topic of nontuberculous mycobacterial disease was a true example of Aristotelian science. Previously, only a few experts worldwide had compiled empirical data and disseminated knowledge on the subject, which was based upon meticulous observations in small series or case studies from the 1950s onwards [3]. These studies demonstrated the manifold particularities of M. avium complex disease and others as compared with tuberculosis, and also showed how even nontuberculous mycobacterial lung diseases alone, quite apart from manifestations in other organs, appear in widely varying forms. To this day, an ever increasing number of reports on uncommon or recently detected and potentially pathogenic species with strange names deepen the impression that we are dealing with an intricate matter.