Pulmonary Cavitary Lesions: Mycobacterium Abscessus or Malignancy?

Abstract 56-year-old female with a history of left lower lobe lung adenocarcinoma s/p left lower lobectomy (2011) with recurrence of stage IV cancer, COPD on 2 L nocturnal oxygen, active tobacco use, and treated chronic hepatitis C who presented with a progressively worsening productive cough of brown sputum, hemoptysis, and night sweats. The patient was hemodynamically stable upon arrival to the ED. Of note, she was undergoing work-up outpatient due to concern for recurrence of the lung adenocarcinoma. She was admitted for further work-of multiple cavitary pulmonary lesions that were seen on CT scan. She underwent a biopsy for PD-L1 of one of the pulmonary lesions seen on imaging which revealed necrotizing granulomatous inflammation with rare acid-fast bacilli without evidence of malignancy. Initially, two AFB smears and MTB PCR testing were negative. However, five days after discharge, AFB cultures were found to grow Mycobacterium abscessus and she was started on cefoxitin 2 g TID, amikacin 10 mg/kg daily, and PO linezolid 300 mg daily in addition to omadacycline 300 mg daily after FDA approval was obtained. Additionally, NGS testing later revealed elevated PD-L1 expression (90%), and the patient was started on pembrolizumab. A few months later, linezolid was discontinued, and the patient was started on clofazimine after FDA approval was obtained. After approximately two months of treatment, all antibiotics were discontinued due to side effects including visual disturbance, rash, and confusion. This case highlights the steps taken to evaluate pulmonary cavitary lesions and illustrates the use of the novel drugs omadacycline and clofazimine used to treat what turned out to be a case of Mycobacterium abscessus.