Host susceptibility factors in mycobacterial infection - Genetics and body morphotype

Mycobacteria traditionally have been thought of as virulent pathogens that cause disease by respiratory contagion. Recognition of nontuberculosis mycobacterial (NTM) disease in otherwise normal hosts however, has shown that host susceptibility factors play a key role in infection. Identification of multiple defects in the INFgamma and interleukin-12 pathways, including impaired signaling through the transcription factors STAT1 and NFkappaB, has elucidated the pathways involved in disseminated disease better. In patients with pulmonary Mycobacterium avium complex disease, a characteristic body morphotype suggests that subtle immune defects or polymorphisms may underlie susceptibility. Although there are distinct differences between tuberculosis (TB) and NTM, detection of genetic and phenotypic associations with the latter also may provide insight into risk factors for TB.