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.