Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 55 3 2026 10 04 40750 40750 Ehsan Esmaeili Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Hasti Kamali Sarvestani Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Alireza Abdollahi Department of Pathology, Imam Hospital Complex, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Mohammadreza Salehi Infectious Diseases Department, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran Mehdi Yaseri Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Shahram Mahmoudi Department of Parasitology and Mycology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Fuad Haghighat 3- Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Seyed Jamal Hashemi Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Roshanak Daie-Ghazvini Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Kazem Ahmadikia Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Pegah Ardi Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2025 09 19 2026 07 09 Abstract Background: Pulmonary fungal infections are increasingly recognized as significant contributors to respiratory disease, particularly among immunocompromised patients. Despite their clinical importance, differentiating colonization from true invasive infection remains a major diagnostic challenge. Methods: In this multicenter cross-sectional study (June 2024–May 2025), 568 adults with suspected lower respiratory tract infections from three tertiary hospitals in Tehran were evaluated. Respiratory specimens underwent microscopy, culture, and galactomannan (GM) testing. Yeast isolates were identified using multiplex PCR (YEAST PLEX). Clinical characteristics, comorbidities, and radiological findings were analyzed. Results: Fungi were detected in 342 patients (60.2%). Fungal-positive patients were older than negatives (52.4 ± 15.7 vs. 49.1 ± 17.3 years, p = 0.038). Candida species (56.4%) predominated, followed by Trichosporon (24.9%), Aspergillus (12.9%), Pneumocystis (3.2%), and other molds. Hemoptysis was significantly more common in fungal-positive patients (21.1% vs. 12.4%, p = 0.019), whereas cough, fever, and pleuritic chest pain showed no differences. Cavitary or nodular infiltrates were associated with fungal positivity (31.6% vs. 14.6%, p < 0.001), while ground-glass opacities and consolidations were not. GM testing was positive in 73.8% of Aspergillus-positive patients and 9.3% of controls (p < 0.001), with higher mean optical density indices in infected cases. Conclusion: Pulmonary fungal infections are common and underrecognized in respiratory disease. BAL sampling, GM testing, and radiologic correlation provide valuable tools for distinguishing true infection from colonization, particularly in older and immunocompromised patients. https://ijph.tums.ac.ir/index.php/ijph/article/view/40750