Cytomorphology Unmasks Occult Mycobacterium colombiense Coinfection in Talaromyces marneffei Infection: First Case Report and Systematic Review of 26 Cases (2008-2024)

Background Talaromyces marneffei ( T. marneffei ) is a well-recognised opportunistic pathogen in immunocompromised hosts, while Mycobacterium colombiense ( M. colombiense ) represents an emerging non-tuberculous mycobacterium. Coinfection with these pathogens has never been reported, particularly in immunocompetent individuals. Methods We present the first documented case of T. marneffei - M. colombiense coinfection in an immunocompetent host, integrated with a PRISMA-compliant systematic review of global M. colombiense infections (2008–2024). Case and Results A 50-year-old immunocompetent woman presented with chest wall osteomyelitis, a non-healing wound, and persistent fever. Metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid uniquely detected T. marneffei . However, comprehensive testing (including mNGS and microbiological culture) of blood, wound exudate, sputum, and biopsies yielded no significant pathogens, and voriconazole monotherapy proved ineffective. Cytomorphological analysis of wound exudate revealed phagocytosed bacilli unstained by Wright-Giemsa within phagocytes, prompting targeted acid-fast staining and mycobacterial culture, which subsequently identified M. colombiense by MALDI-TOF MS. Systematic analysis of 26 global M. colombiense cases revealed: Dominant lymphatic-pulmonary involvement(Lymph nodes: 73.1%, Lungs: 65.4%,); Pronounced osteocutaneous tropism (Bone/Joint: 38.5%, Skin: 38.5%); Substantial mortality(23.1%, 6/26). Conclusions This study establishes: (1) The first evidence of T. marneffei - M. colombiense coinfection in immunocompetent hosts; (2) The crucial role of cytomorphology in overcoming coinfection blind spots; (3) A diagnostic T-MAP algorithm (Cytomorphology- morphology-guided targeted testing, followed by molecular and culture confirmation); (4) M. colombiense 's distinct clinical profile characterised by significant osteocutaneous tropism and high mortality (23.1%).