A CASE OF MAC IN A PATIENT WITH CHRONIC SILICOSIS

Abstract

SESSION TITLE: Medical Student/Resident Occupational and Environmental Lung Disease SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Our patient is a 32-year-old male with chronic silicosis who presented with one week of worsening dyspnea and cough in the setting of a 40 pound weight loss over 3 months. CASE PRESENTATION: The patient was diagnosed with silicosis in 2015 (Image 1) in the setting of prolonged work with cutting porous stone without use of PPE; he had a negative mycobacterial work-up then. He was lost to follow-up and continued to work until one week prior to this presentation. On hospital presentation he was found to be febrile, severely cachectic, using accessory muscles for respiration, and with fine bilateral inspiratory crackles diffusely. He was subsequently admitted to the ICU for hypercapnic and hypoxemic respiratory failure requiring non-invasive ventilation (NIV). CT findings suggested progressive massive fibrosis (PMF) with eggshell calcifications of mediastinal lymph nodes; however, a cavitary infectious process could not be ruled out (Image 2 and 3). He was started on empiric antibiotics for bacterial pneumonia. Laboratory testing revealed negative bacterial, fungal, and viral sputum/blood cultures. He showed marginal improvement in respiratory status after initiating NIV and completing antibiotics. Although the initial AFB sputum smears were negative, two weeks later two separate AFB cultures each grew Mycobacterium Avium Complex (MAC). He was fully weaned off NIV after starting anti-mycobacterial therapy. Given the imaging and his clinical improvement, this decompensation was thought to be secondary to PMF with MAC superinfection. DISCUSSION: Silicosis occurs following chronic occupational exposure to aerosolized silica from mining, stone cutting, or sandblasting. Patients often are asymptomatic despite abnormal x-ray findings. Imaging of chronic silicosis typically follows nodular patterns of inflammation (which was noted on our patient's initial diagnosis) and in more acute presentations ground-glass opacities and crazy paving have been described. Our patient's clinical presentation and CT findings of diffuse coalescent densities and cavitations led us to consider PMF and mycobacterial disease over simple silicosis. PMF is a rare, and in most cases irreversible, complication of silicosis defined as conglomeration of dense fibrosis preferentially involving the upper lung lobes. Eggshell calcifications of lymph nodes are often described. Mycobacterial infection is also a rare complication of silicosis, classically with mycobacterium tuberculosis (TB); however there have been many case reports with silicosis patients developing MAC infections. These mycobacterial infections present with constitutional and TB-like symptoms such as weight loss. CONCLUSIONS: Progressive massive fibrosis in silicosis is a rare complication that leads to severe structural lung disease and respiratory failure. Mycobacterial superinfection, including MAC, should be considered in decompensated patients with silicosis. Reference #1: Jiro Fujita,Takumi Kishimoto,Yuji Ohtsuki,Eriko Shigeto,Takayuki Ohnishi,Masahiro Shiode,Yasufumi Yamaji,Ichizo Suemitsu,Ichiro Yamadori,Shuji Bandoh,Kazutaka Nishimura,Toshiharu Matsushima,Toshihiko Ishida. Clinical features of eleven cases of Mycobacterium avium-intracellulare complex pulmonary disease associated with pneumoconiosis. Respir Med. 2004 Aug;98(8):721-5. DISCLOSURES: No relevant relationships by Neel Bhan, source=Web Response No relevant relationships by Nicola Hanania, source=Web Response No relevant relationships by Lauren Nicholas Herrera, source=Web Response No relevant relationships by Hal Zhang, source=Web Response