B72-10 Cavitary Blastomycosis in an Immunocompetent Adult: A Diagnostic Challenge in an Underrecognized Region

Abstract Introduction Pulmonary blastomycosis is a fungal infection acquired through inhalation of spores from moist soil. It is most prevalent in the Great Lakes, Ohio Valley, and upper Midwest. Although historically uncommon in the Southeast (about 6%), recent data show a 2.4 fold increase from 2013 to 2023. Recognition remains challenging because imaging findings often mimic bacterial infection or malignancy, appearing as consolidations, masses, nodules, or, rarely, cavitation. This case highlights the diagnostic difficulty of blastomycosis in a low-incidence region, where overlapping radiologic features and absence of classic risk factors can delay diagnosis and treatment. Case Presentation A 34-year-old woman with gastric reflux and chronic pain on methadone presented with one week of worsening shortness of breath and nausea. Non-contrast chest CT revealed a 4 cm cavitary lesion in the right lower lobe. Initial laboratory testing showed leukocytosis, a positive Mycoplasma pneumoniae IgM, and a negative QuantiFERON test. She had no history of smoking, recent travel, gardening, or outdoor exposure, and denied sick contacts or underlying lung disease. Without clear risk factors, she was initially diagnosed with sepsis secondary to cavitary pneumonia and started on broad-spectrum antibiotics. Despite treatment, symptoms persisted, and three weeks later she was readmitted with acute dyspnea due to a spontaneous tension pneumothorax, requiring emergent chest tube placement. Pleural bacterial cultures were negative, while fungal culture later grew Blastomyces. Video-assisted thoracoscopic surgery was performed for persistent pneumothorax and a pleural biopsy further confimed the diagnosis, all three weeks after her initial presentation. She was started on a six-month course of isavuconazole. At eight week follow up, she showed marked clinical improvement and partial resolution of the lesion on repeat imaging. Discussion Cavitary lung lesions often suggest tuberculosis (50%), bacterial abscesses (20%), or malignancy (20%). However, fungal infections (5-10%) should be considered in the differential diagnosis, especially as the geographic distribution of blastomycosis expands. National incidence has risen from 0.4 to 1.3 cases per 100,000 person-years, with emerging cases in the southeastern U.S., particularly Alabama. Although reportable in several states, blastomycosis remains non-reportable in Alabama, likely contributing to underdiagnosis and underestimation of its true burden. Raising clinical suspicion for fungal etiologies, even in non-traditional regions, is key to minimize diagnostic delays. Early recognition and antifungal therapy can prevent unnecessary antibiotic exposure and improve outcomes. This case highlights the rarity of fungal cavitary disease, the rising incidence of blastomycosis, and the need for awareness in underrecognized regions like Alabama. This abstract is funded by: None