Sinus Disease Caused by Lophomonas Sp. In an Immunocompetent Patient: A Case Report

Lophomonas blattarum is a multiflagellated protozoan commensal commonly found in the intestines of cockroaches and termites. Human infection is rare and, in most cases, affects the lower airways and is closely associated with immunocompromised individuals. This parasite has been described in respiratory secretion samples from patients with pneumonia unresponsive to usual treatments and in patients with poorly controlled asthma. A 41-year-old female patient, previously healthy, participated in a military expedition in the Amazon region in May 2023, where she was bitten by an unidentified insect in the right popliteal fossa, evolving with a small ulcerated lesion. She was referred for investigation of cutaneous leishmaniasis in an infectious disease service in Rio de Janeiro, with indeterminate serology and detectable PCR. Treatment with meglumine antimoniate was initiated, but due to QT interval prolongation, therapy was completed with liposomal amphotericin B. Despite improvement of the skin lesion, the patient developed epistaxis and oppressive sensation over the left maxillary sinus. CT scan of the paranasal sinuses revealed opacification of the left maxillary, frontal, and ethmoid sinuses. ENT evaluation and nasofibroscopy revealed a friable polypoid nasal lesion with mucopurulent secretion. Biopsy was performed and empirical treatment for bacterial rhinosinusitis initiated. Histopathology showed acute and chronic inflammatory process with eosinophilia and plasmacytosis, without granulomas or neoplasia. Culture in NNN medium revealed multiflagellated protozoa of the genus Lophomonas sp. The patient was treated with metronidazole 500 mg every 6 hours for 30 days, with complete symptom resolution. This report suggests a possible first case of sinus disease caused by this parasite in Brazil, reinforcing the possibility of infection at sites beyond the lower airways. It also highlights the importance of considering Lophomonas sp. infection as a differential diagnosis for insidious sinus disease, even in immunocompetent individuals.