Community-acquired Pneumonia: Diagnostic Challenges in Non-immunocompromised Patients

Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality worldwide, affecting individuals outside health care settings. Streptococcus pneumoniae is the predominant pathogen, although regional and socioeconomic factors significantly influence epidemiology, resistance patterns, and outcomes. Diagnosis relies on clinical evaluation supported by imaging, microbiology, and biomarkers, yet presentations are highly variable across age groups and comorbidities. Chest radiography remains the cornerstone for initial assessment, while high-resolution CT (HRCT) offers superior sensitivity for early detection and complications. Typical bacterial pathogens (eg, S. pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae) produce lobar or bronchopneumonic consolidations, whereas atypical organisms (Mycoplasma, Chlamydia, Legionella) and viruses often yield diffuse ground-glass or interstitial patterns. Fungal and mycobacterial infections must also be considered, particularly in endemic regions. Radiologic-pathologic correlation is essential to differentiate CAP etiologies, guide management, and identify complications such as cavitation, empyema, or necrosis. Understanding these imaging patterns within global and clinical contexts is critical for improving diagnostic accuracy and optimizing patient outcomes.