A Rare Mycobacterial Infection Presenting as Worsening Cavitary Lung Lesions

Abstract Introduction: Mycobacterium malmoense is a slow-growing, non-tuberculous mycobacterium which primarily causes pulmonary disease. M. malmoense is acquired through environmental exposure to contaminated soil or water in individuals with impaired cell immunity. M. malmoense infection may cause extrapulmonary manifestations including cervical adenitis, tenosynovitis, and disseminated disease. Our literature search revealed extremely few cases reported on M. malmoense causing cavitary lesions. We present a case of a patient with hemoptysis and worsening bilateral lung cavitary lesions where sputum culture isolated M. malmoense. Case presentation: A 58-year-old male with a past medical history of hypertension, 80-pack-year smoking history, polysubstance abuse with methamphetamine, cannabis, benzodiazepines, hepatitis C, COPD, and chronic cavitary lung lesions was admitted to the hospital secondary to hemoptysis. He had an initial episode of hemoptysis approximately one year ago which self-resolved after six days. He was scheduled to receive outpatient bronchoscopy for his chronic cavitary lesions though missed follow-up. Two days before the current admission, the patient had worsening cough and bloody sputum. He denied chest pain, night sweats, weight loss, fever, or chills. Computerized tomography (CT) chest showed a new right lower lobe cavitary nodule measuring 3.4 cm x 2.8 cm and unchanged bilateral apical cavitary lung lesions. Our patient was started on IV piperacillin-tazobactam and vancomycin. He had approximately 150 ml of hemoptysis in 24 hours therefore received inhaled tranexamic acid. Sputum smear was positive for acid fast bacilli. Quantiferon TB and HIV testing were negative. Sputum cultures grew Mycobacterium malmoense. Unfortunately, the patient refused any further treatment. Discussion: Mycobacterium species are seen in patients with underlying lung disease or immunocompromised states. Infection is diagnosed by clinical, radiological, and microbiological workup. Microbiological workup includes two separate sputum samples or via transbronchial biopsy or bronchial wash. The most common radiological finding include thick-walled cavitary lung lesions in the upper lobes and underlying pulmonary fibrosis. This Mycobacterium species has high antimicrobial resistance. As per the current ATS and IDSA guidelines, multidrug treatment with macrolides, ethambutol, and rifamycin for a duration of 12 months is indicated. Conclusion: Non-TB Mycobacterium infrequently causes disease, though in susceptible or immunocompromised individuals, it can cause serious respiratory infections. M. malmoense infection still carries a high mortality risk, so careful and early diagnosis is important to improve outcomes. It is important to recognize patients with non-resolving radiographic imaging as well as atypical and persistent infections that do not improve with standard treatment.