Endobronchial Lesions in an Immunocompromised Host

To the Editor: Over the past decade, we have seen a variety of monoclonal antibodies emerging to modulate patients’ immunologic response. These medications can potentially make patients vulnerable to pulmonary infections that are otherwise uncommon.1 Rapidly growing mycobacteria are microorganisms that may proliferate under immunosuppression. Within this group of microorganisms, Mycobacterium fortuitum is not commonly isolated in respiratory specimens as opposed to Mycobacterium abscessus, the most pathogenic of the rapidly growing mycobacterias and more frequently seen causing pulmonary infections.2 We describe a patient with peculiar unilateral endobronchial lesions in which M. fortuitum was isolated twice by bronchoscopy, bronchoalveolar lavage (BAL), and endobronchial forceps biopsy. CASE SUMMARY A 67-year-old woman was admitted for chronic obstructive pulmonary disease exacerbation. She was a former smoker with past medical history mainly relevant for severe chronic obstructive pulmonary disease (group D) and rheumatoid arthritis treated with tocilizumab, a humanized monoclonal antibody against the interleukin-6 receptor. Computed tomography of the chest showed multiple nodular, well-defined opacities dispersed in the left lung and bronchiectasis. In the setting of an immunocompromised host; bronchoscopic evaluation was performed and showed multiple exophytic, pedunculated, pearl-like, colored endobronchial lesions throughout several pulmonary segments of the left lung (Fig. 1). BAL was performed, and M. fortuitum was isolated on 2 different occasions. Endobronchial forceps biopsies of the lesions were performed and the tissue analysis showed 3 irregular fragments of tan/pink soft tissue measuring up to 2 mm. Light microscopy showed benign bronchial wall mucosa with associated acute and chronic inflammation and dystrophic calcifications. Acid-fast stain showed the presence of mycobacteria. There was no evidence of granulomas, fungal organisms, or neoplasms. The patient was treated with doxycycline and trimethoprim/sulfamethoxazole for a total of 9 months. Repeat airway inspection at 4 months of therapy showed resolution of the endobronchial lesions but persistence mycobacterial growth in the BAL. The Mycobacterium was finally eradicated at 7 months of antibiotic treatment in both BAL and endobronchial lesions.FIGURE 1: Endobronchial lesions in the left lung (A–D). Computed tomography of chest showing multiple nodular well-defined opacities dispersed in the left lung (E). Nodularity better seeing in the maximum intensity projection reconstruction (F).DISCUSSION Endobronchial lesions are often seen during bronchoscopic evaluation and endobronchial biopsy for tests including histology and microbiology is appropriate. Staining for acid-fast bacilli is recommended, especially in immunocompromised patients. M. fortuitum has not previously been described as causing endobronchial lesions. This bacterium is unique among mycobacteria, as it has the ability and propensity to produce biofilm to protect itself. This film is composed of bacteria that have undergone a physiological and phenotypic shift from their motile state to a stationary and matrix-producing state.3 Our case adds to the literature regarding pulmonary infections with rapidly growing mycobacteria such as M. fortuitum. It is important to highlight that M. fortuitum has the ability to form biofilm and may not present with the usual granulomatous inflammation as with other mycobacteria. A high index of suspicion is required in immunosuppressed patients as infections caused by M. fortuitum may not be easily distinguishable from more typical infections on imaging studies and yet they require very different treatment.4 In such cases, bronchoscopic evaluation and forceps biopsy of any visible endobronchial lesions combined with BAL is often indicated to achieve an accurate diagnosis. David Abia-Trujillo, MD Anna Kornafeld, MD Sebastian Fernandez-Bussy, MDDivision of Pulmonary, Allergy, and Sleep Medicine, Mayo Clinic, Jacksonville, FL