CF patients are at increased risk for NTM MAC infections

NTM have been isolated from the sputum of adults and children with CF with increasing frequency since the 1990s. The increase in detection may be partially attributed to improvements in microbiological detection and enhanced surveillance, but there is also evidence of a rise in the frequency of NTM infections in this population and increasing prevalence with age. The most common NTM identified in people with CF are species of the Mycobacterium avium complex (including M avium, M intracellulare, and Mycobacterium chimaera), accounting for more than 70% of NTM-positive sputum cultures. The next most common NTM identified in the sputum of people with CF are species of the Mycobacterium abscessus complex (including M abscessus subspecies abscessus, M abscessus bolletii, and M abscessus massiliense.

Several risk factors have been identified that predispose people with CF to NTM infections, including the presence of structural lung disease (eg, bronchiectasis) and mucociliary damage, which results in poor airway clearance. Additionally, mutations in the CF transmembrane conductance regulator gene (CFTR) resulting in abnormal bronchial epithelial ion and water transport may contribute to the increased incidence in this population. The incidence of NTM infections in people with CF is much higher than in the general population, but interestingly, studies of patients with M intracellulare infections who do not have CF have demonstrated an increased incidence of single CFTR mutations, providing support for this proposed mechanism (choice A is correct).

T-lymphocyte-mediated immunity is impaired in individuals with AIDS, immunosuppression for organ transplantation, and hematologic malignancies, predisposing these individuals to infection due to intracellular organisms such as Mycobacteria. This is not typical of people with CF (choice B is incorrect).

Patients with neutrophil dysfunction (eg, chronic granulomatous disease) and neutropenia are more likely to develop pulmonary infections caused by endogenous bacterial flora, molds, and Nocardia species (choice C is incorrect).

Mutations in the FBN1 gene (encoding fibrillin-1) result in Marfan syndrome, which has been associated with structural lung disease or the development of NTM lung disease. FBN1 is not associated with CF (choice D is incorrect).