Probable Disseminated Mycobacterium avium Complex Infection in an Apparently Immunocompetent Patient: A Case Report and Literature Review

Disseminated Mycobacterium avium complex (MAC) infection is rare in immunocompetent hosts. This often leads to diagnostic delays. We report a challenging case of an apparently immunocompetent patient with pulmonary lesions, osteomyelitis, and skin ulcers. While routine cultures were pending, metagenomic next-generation sequencing (mNGS) rapidly identified MAC, enabling timely treatment. Subsequent culture and species identification confirmed the pathogen as Mycobacterium colombiense . Systematic reviews since 2000 have shown that skeletal and pulmonary involvement are common in this population. Diagnosis has gradually incorporated molecular biological techniques, and with timely treatment, patient outcomes are generally favorable. Our findings highlight the limitations of traditional microbiology and demonstrate that mNGS is a vital adjunctive tool for slow-growing pathogens. We conclude that disseminated MAC should be considered in refractory multifocal infections, even without recognized immunodeficiencies. Early molecular diagnosis, individualized multidrug therapy, and rigorous follow-up are essential for clinical remission.