Identification of Mycobacterium leprae and Mycobacterium lepromatosis Cases with Broad-Range Molecular Assays at a Single Large Reference Laboratory

Definitively diagnosing Hansen's disease (HD) is challenging, but molecular methods can provide species identification of the causative mycobacteria (Mycobacterium leprae and Mycobacterium lepromatosis). Most studies have investigated targeted assays, and the performance of broad-range molecular approaches remains unknown. This study evaluated a multilocus (hsp65, 16S ribosomal RNA, and rpoB) broad-range polymerase chain reaction (PCR) assay in detecting HD-associated mycobacteria at a single large reference laboratory in the United States from 2009 to 2024. We identified 148 positive samples from 137 patients submitted from 26 states. Mycobacterium lepromatosis was identified in 8 of 137 patients (5.8%), and M. leprae was identified in the rest. Although most samples were skin biopsies (∼90%), 10 samples (7.9%) represented atypical locations, including bone marrow and liver. Half of all samples were identified by only a single target (n = 72/146 samples, 49.3%), and rpoB was the most likely to be positive (n = 123/146 samples, 84.2%). Overall, broad-range PCR successfully identified HD-associated mycobacteria, including M. lepromatosis, from skin and atypical anatomic sites, and it should be considered more frequently in the evaluation of suspected cases.