Diminished Susceptibility of African–Americans to Non-tuberculous Mycobacterial Disease

The incidence of three granulomatous response diseases—sarcoidosis, tuberculosis, and non-tuberculous mycobacterial pulmonary disease—differ markedly in African–Americans versus Caucasians. In reviewing a large compendium of non-cystic-fibrosis bronchiectasis, we noted that complicating infection with non-tuberculous mycobacteria was relatively infrequent among individuals of African–American descent, confirming previous observations of their inherent resistance. Disease-specific variance among African–Americans in the efficacy of their granulomatous response suggests a nexus, a mediating, immunological mechanism. Environmentally conditioned selection of SLC11A1 (Nramp1) alleles may account for this ethnic variance.