RESUMEN
BACKGROUND: Chronic sinusitis is one of the most common otolaryngological diagnoses. Allergic fungal sinusitis and eosinophilic mucin rhinosinusitis can easily be misdiagnosed and treated as chronic sinusitis, causing continuing harm. AIM: To better identify and characterise these two subgroups of patients, who may suffer from a systemic disease requiring multidisciplinary treatment and prolonged follow up. METHODS: A retrospective, longitudinal study of all patients diagnosed with allergic fungal sinusitis or eosinophilic mucin rhinosinusitis within one otolaryngology department over a 15-year period. RESULTS: Thirty-four patients were identified, 26 with eosinophilic mucin rhinosinusitis and 8 with allergic fungal sinusitis. Orbital involvement at diagnosis was commoner in allergic fungal sinusitis patients (50 per cent) than eosinophilic mucin rhinosinusitis patients (7.7 per cent; p < 0.05). Asthma was diagnosed in 73 per cent of eosinophilic mucin rhinosinusitis patients and 37 per cent of allergic fungal sinusitis patients. CONCLUSION: Allergic fungal sinusitis and eosinophilic mucin rhinosinusitis have the same clinical presentation but different clinical courses. The role of fungus and the ability to confirm its presence are still problematic issues, and additional studies are required.