Virginia Research Day 2025

Medical Resident Research Case Reports

10 Atypical Mycobacterial Avium Intracellulare Infection in the Immunocompetent Host

Diana Duong, DO, PGY3; Nistha Acharya, MD, PGY2; Kimberly Bird, MD; Fahid Alghanim, MD Corresponding author: diana.duong@LPNT.net Sovah Health – Danville Department of Internal Medicine Residency, Division of Pulmonology and Critical Care Medicine

the patient had no associated symptoms, but she later on developed night sweats and occasional dyspnea with exertion. CT chest with contrast revealed right upper lobe cavitary lesion measuring up to 4.1 cm with bilateral tree-in-bud nodularities and prominent nodules in the right lower lobe measuring up 1.6 cm in maximal dimension. A QuantiFERON test was negative. Navigational bronchoscopy was performed in April 2024 and pathology revealed no evidence of malignancy; however, there was evidence of granulomatous changes. Acid-fast bacilli culture grew Mycobacterium Avium intracellulare. The patient was referred to Infectious Disease and started on azithromycin 500 mg daily, rifampin 600 mg daily, and ethambutol 900 mg daily. Decision was made to later add on intravenous (IV) amikacin twice a week. Duration of oral antibiotics will be for 18 months and IV antibiotics for 2-3 months. Discussion: This case highlights an interesting and rare phenomenon of MAC lung disease in an immunocompetent host. MAC lung

disease is typically seen in individuals who are immunocompromised, have underlying lung disease, or of elderly age; none of which our patient exhibits. The patient was likely exposed during her travels abroad. There are two types of MAC lung disease: nodular bronchiectatic and fibro cavitary disease. Nodular bronchiectatic type develops in the small airways and air sacs and is typically seen in thin females who do not smoke. Fibrocavitary disease type is the more severe form of MAC due to its cavitary nature and is typically seen in individuals who smoke or have emphysema. MAC infection can appear similar to tuberculosis (Tb) on imaging; however, causative agent and diagnosis modality is different. Identification of MAC lung disease is important to prevent disseminated MAC; especially in at-risk populations as complications can lead to death.

Introduction: Mycobacterium avium complex (MAC) is a non-motile, spore-forming, gram-positive acid-fast bacillus that is the most common cause of non-tuberculosis mycobacterial pulmonary disease (NTM-PD). Acquisition of MAC is via inhalation, thus making the pulmonary system the most common site of infection. Prevalence of MAC infections in the United States varies from 1.4-6.6 per 100,000 individuals. MAC can be found in the environment in soil, water, and dust. Risk factors for MAC include chronic lung disease, CD4 count less than 50 in AIDS patients, immunosuppression, mitral valve prolapse, and thoracic and skeletal abnormalities. Dissemination of MAC can occur in those with AIDS and immunosuppression. Case: We present a 38-year-old female with a 20+ year history of tobacco use who was referred to Pulmonology for abnormal computed tomography (CT) findings and chronic cough. History revealed the patient returned from Tanzania in November 2023 and the nonproductive cough started then. Initially,

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