[Allergic fungal rhinosinusitis: A diagnosis to evoke].

Among fungal infections of the nasal sinuses, allergic fungal rhinosinusitis is a recently described, relatively rare and little known pathology. Its diagnosis is based on: clinical criteria (it occurs in young immunocompetent patients, often associated with bilateral nasosinusal polyposis); pathological criteria (allergic mucin: eosinophilic mucus without invasion of the sinusal mucosa and observation of fungal hyphae on surgical samples); biological criteria (hypereosinophilia, total and specific antifungal IgE); and radiological criteria. The combination of tomodensitometry (heterogeneous hyperdense and diffuse filling of nasosinusal cavities with expanded borders and a distended appearance of the bony wall), and MRI scan (extensive character and lesional signal [hypo and asignal T1 and T2], and cerebriform aspect of the fungal process) strongly suggests the diagnosis. It is important to distinguish the most typical forms, as well as unusual forms of allergic fungal rhinosinusitis. Main differential diagnoses are represented by other forms of fungal nasosinusal infections with different treatment and prognosis.