Probable Autochthonous Transmission of Mycobacterium lepromatosis in the Pacific Northwestern United States

Mycobacterium lepromatosis (M. lepromatosis), first described in 2008 as another mycobacterial species that causes Hansen's disease, has mainly been reported in Mexico, Central America, and the southern United States; however, its disease spectrum and distribution remain unclear. A diagnostically challenging case that represents a likely autochthonous M. lepromatosis acquisition in the United States is reported in the present study. A 75-year-old immunocompetent man who had not traveled outside the Pacific Northwest developed an erythematous, ulcerating left thigh plaque, followed by three proximal sporotrichoid nodules. Biopsies revealed granulomatous inflammation with negative acid-fast stain results. Broad-range nontuberculous mycobacterial polymerase chain reaction testing identified M. lepromatosis in the sentinel ulcer and possible Mycobacteroides chelonae coinfection in the proximal nodule. The patient improved with multidrug therapy. Clinicians in the United States should keep Hansen's disease in the differential diagnosis, even for patients without international travel. Additional research is needed to clarify the phenotypic spectrum and geographic distribution of this pathogen.