Critical Care Medicine | 2019
1101: NOT ALL THAT SHINES IS GOLD MYCOBACTERIUM KANSASII, A SOLITARY PULMONARY NODULE
Abstract
Learning Objectives: Often found in tap water in endemic areas, Mycobacterium kansasii is one of the most common nontuberculous mycobacterium (NTM) species. It predominates along the southeastern, southern coastal and central plains states. The disease incidence increases with age, with the majority presenting >50 years old. Risk factors include COPD, underlying malignancy, immunosuppressive medications and many others. Radiographically, the organism forms thin-walled cavities in the upper lobes and clinically resembles tuberculosis. Rarely, M. kansasii presents as a solitary pulmonary nodule of unknown significance, requiring extensive diagnostic workup. Methods: A 61-year old male with a past medical history of tobacco use and COPD was found to have an incidental 2.7 cm, spiculated right upper-lobe (RUL) pulmonary nodule with surrounding air bronchograms and ground-glass opacities on routine lung screening. The nodule proved to be hypermetabolic and slightly larger in size on subsequent positron emission tomography (PET) scan. During follow up video-assisted thoracoscopic surgery (VATS) wedge resection, an area of pleural tenting and a discrete mass was identified. Purulent, caseating material was present upon dissection of the mass. Surprisingly, pathology performed on the specimen indicated positive acid-fast bacilli and granulomatous tissue. Ultimately, cultures finalized and the patient was diagnosed with Mycobacterium kansasii pulmonary disease. No pharmacologic treatment was administered given the lesion was removed and the patient was asymptomatic. Results: Radiographic findings of NTM are variable and include cavitary lesions, infiltrates, bronchiectasis and rarely small nodules. Specifically, with regard to M. kansasii infection, >90% of patients demonstrate thin-walled cavitary disease in the upper lobes. Solitary nodules have been described but are far less common. NTM pulmonary nodules (NTMPNs) are a form of solitary pulmonary caseating granulomas (SPCGs) and the clinical significance of these NTMPNs is still being investigated. Specifically, with regards to indication for treatment because the prognostic significance of these nodules is uncertain. In an asymptomatic COPD patient, a solitary, spiculated and hypermetabolic lung nodule is certainly malignancy until proven otherwise. This case, however, serves as a reminder that Mycobacterium kansasii infection can, on rare occasion, manifest in such a way.