First molecular evidence of neglected Lophomonas infection among patients with chronic sinusitis undergoing functional endoscopic sinus sampling: a registry based-study

Lophomonas spp. are emerging protozoan pathogens documented in lower respiratory tract infections, yet their potential involvement in upper respiratory conditions, particularly chronic sinusitis, remains entirely unexplored. Unfavorably, chronic sinusitis often proves refractory to standard antibacterial and antifungal therapies, a treatment-failure pattern that raises the possibility of overlooked protozoal etiologies. To date, no registry-based studies have investigated Lophomonas in sinus specimens, and the parasite is not considered in the differential diagnosis of chronic sinusitis. This study aimed to address this knowledge gap by investigating the presence of Lophomonas infection through both microscopic and molecular methods in patients with chronic sinusitis refractory to conventional therapy in northern Iran. Sinus lavage fluid (SLF) specimens were collected from 30 patients with clinically and radiologically confirmed chronic sinusitis at two teaching hospitals. Samples were analyzed using direct light microscopy and an in-house conventional PCR assay targeting the genus-specific small subunit ribosomal RNA gene (SSU rRNA). Lophomonas was detected in 14 out of 30 patients (46.6%; 95% CI: 30.2%–63.9%). Perfect diagnostic concordance (100%) was observed between microscopy and PCR. No statistically significant associations were found between infection status and demographic variables or recorded comorbidities. The most common clinical presentations included headache, nasal congestion, hyposmia, rhinorrhea, and post-nasal drip (PND), with pansinusitis being the predominant computed tomography finding.