Abstract Introduction Mycobacterium kansasii is a slow-growing, acid-fast bacillus known to cause cavitary lung lesions. Its presentation is similar to Mycobacterium tuberculosis and requires microbiological identification to differentiate the two. Most patients have preexisting pulmonary conditions, such as chronic obstructive lung disease. Description of Case A 61-year-old male with history of T3N0M0 squamous cell carcinoma of the soft palate, status-post cisplatin chemotherapy with concurrent radiation three years prior, was found to have a right upper lobe peribronchial lesion on computed tomography (CT) angiography as part of a chest pain evaluation. Subsequent positron emission tomography scan showed a 1.1 cm cavitary lesion in the right upper lobe of the lung. CT-guided biopsy revealed necrotizing granulomatous inflammation and rare acid-fast bacilli. Bronchoscopy with bronchoalveolar lavage (BAL) was performed with culture identifying M. kansasii. He was referred to infectious disease but was lost to follow-up and did not initiate treatment. Approximately three months after his BAL, he was admitted to the intensive care unit with septic shock. CT of the chest showed progression to a 10 cm thick-walled cavitary lesion and multifocal consolidative opacities. The patient required intubation for airway protection and was started on broad-spectrum antibiotics. Repeat respiratory cultures revealed polymicrobial co-infection with Providencia rettgeri, Pseudomonas aeruginosa, and Achromobacter xylosoxidans. Ultimately, his family elected to pursue comfort care measures, and medical care was withdrawn. Discussion Mycobacterium kansasii is a nontuberculous mycobacterium causing primarily pulmonary disease. Although categorized as a slow-growing mycobacterium, it has potential for significant virulence. Standard treatment involves isoniazid, rifampin, and ethambutol for 12 months with susceptibility testing. Untreated M. kansasii typically leads to chronic progressive lung disease. Even with appropriate antibiotic therapy, some cases progress. In a study by Liu et al, acid-fast smear grade ≥3, fibrocavitary pattern, age 65, leukocyte count 9000, absence of diabetes, and absence of other mycobacterial co-infections were associated with progression. This case demonstrates the rapid progression of a cavitary lesion from 1.1 to 10 cm over three months with untreated M. kansasii. We hypothesize that the polymicrobial organisms identified contributed to the rate of progression, as his only other risk factor was an elevated leukocyte count 1. This case highlights the urgency of identifying M. kansasii and promptly initiating appropriate antimicrobial treatment to prevent further pulmonary complications. 1. Liu CJ, Huang HL, Cheng MH, et al. Outcome of patients with and poor prognostic factors for Mycobacterium kansasii-pulmonary disease. Respir Med. 2019 May;151:19-26. This abstract is funded by: None
Gaudin et al. (Fri,) studied this question.