C68-23 Conservative Management of Asymptomatic Mycobacterium Colombiense Pulmonary Infection: A Case Report

Introduction Mycobacterium colombiense (M. col) is a rare and clinically challenging non-tuberculous mycobacterium (NTM). Standard management typically involves multi-drug regimens, which are often poorly tolerated. We present a case demonstrating the successful outcome of a conservative, observation-only approach in an asymptomatic patient. Case Presentation A 50-year-old immunocompetent female presented with incidentally discovered pulmonary nodules that had remained radiographically stable over three years. During this period, the patient remained completely asymptomatic, reporting no cough, sputum production, fever, night sweats, or weight loss. Her medical history included an eight-month empirical anti-NTM regimen, which was discontinued due to a severe allergic rash and did not result in radiographic improvement. Physical examination revealed only a benign thyroid nodule. Laboratory investigations demonstrated persistent cytopenias, including anemia, leukopenia, and CD4+ lymphopenia (402 cells/μL), while inflammatory markers remained within normal limits. Chest CT imaging showed characteristic tree-in-bud nodules predominantly in the right upper lobe, accompanied by minimal pleural effusion and nodular pleural thickening. A definitive diagnosis was established through bronchoalveolar lavage fluid analysis, with both culture and metagenomic next-generation sequencing (mNGS) confirming M. col infection. A targeted antimicrobial regimen based on drug susceptibility testing was initiated but discontinued after only four days due to intolerable side effects, including profound fatigue and worsening cytopenias. Through shared decision-making, we elected to adopt a conservative monitoring approach. Subsequent follow-up over 18 months demonstrated complete resolution of radiographic abnormalities and normalization of laboratory parameters, while the patient remained entirely asymptomatic. Discussion This case highlights two critical points. First, it underscores the diagnostic utility of advanced microbiological techniques like mNGS in identifying rare NTM species. Second, and more importantly, it challenges the automatic initiation of treatment for NTM pulmonary disease. The patient’s condition improved spontaneously over 18 months of observation—with resolution of radiographic findings and normalization of laboratory parameters—without any antimicrobial therapy. This outcome suggests that, for a carefully selected subset of patients with mild, non-progressive, and asymptomatic M. col infection, a conservative “watch-and-wait” strategy is a viable and potentially preferable management option, avoiding the substantial toxicity associated with multi-drug regimens. This case provides valuable clinical insight into the natural history of this rare infection and emphasizes the importance of shared decision-making in management.