Mycobacterium abscessus subsp. abscessus Pulmonary Disease: Fatal Case in an Immunocompetent Patient

Nontuberculous mycobacterial pulmonary disease in low-risk patients is rare and typically indolent. We report a case of Mycobacterium abscessus complex (MABC) pulmonary disease in a 71-year-old immunocompetent Italian man who presented with mild dyspnoea that markedly worsened following SARS-CoV-2 infection three months before admission. High-resolution CT showed diffuse small, irregular, predominantly consolidative opacities with peripheral bronchial thickening. Extensive investigations for tuberculosis, fungal infection, other pathogens, and malignancy were negative. Respiratory cultures subsequently yielded MABC, and molecular testing identified a functional erm(41) gene conferring inducible macrolide resistance, consistent with M. abscessus subsp. abscessus. Guideline-based multidrug therapy with intravenous amikacin, tedizolid, clofazimine, and moxifloxacin was initiated. Nephrotoxicity required substitution of intravenous amikacin with an inhaled formulation, followed by ototoxicity and further modification with tigecycline. Despite these adjustments, cultures remained persistently positive. Severe gastrointestinal intolerance and progressive weight loss ultimately led to treatment discontinuation and home oxygen therapy. One year after diagnosis, imaging revealed new cavitary lesions with advanced bilateral disease. The patient died from respiratory failure and severe cachexia. This case shows that MABC infection may follow an aggressive, life-threatening course even in immunocompetent individuals. Antimicrobial resistance combined with treatment-limiting toxicity underscores the urgent need for more effective, better-tolerated therapies and early multidisciplinary management.