Clinical profile of microsporidial keratoconjunctivitis in healthy individuals of China —new species and neglected risk factors

OBJECTIVE: To characterize microsporidial keratoconjunctivitis (MKC) in immunocompetent individuals in Mainland China, including novel etiologies and risk factors. METHODS: A prospective analysis of 20 MKC patients in 2025, including clinical features, pathogens (via corneal scrapings and metagenomic sequencing), risk factors and etc. RESULTS: All patients were misdiagnosed for a median of 1 month. Patients (mean age 28.5 years, 13 F) showed Encephalitozoon hellem (65.0%), E. bieneusi (15.0%, first reported in MKC), and Vittaforma corneae (15.0%). Key risks included bird contact (70.0%, mostly psittacines), contact lens use (40.0%), and water exposure (15.0%). The most common symptom was redness (85.0%); limbal fluorescein positivity occurred in 65.0%. Topical 0.02% PHMB cured 90.0% of 20 cases; one recurrence followed treatment stop. Some E. hellem cases linked to parrots showed potential zoonotic transmission. CONCLUSION: MKC in China involves E. bieneusi and parrot-associated E. hellem. Limbal staining aids diagnosis; PHMB is effective. Zoonotic risks related to Psittacine birds and contact lens use require clinical attention.