[Fibrous dysplasia in a 12-year-old boy with severe house dust mite allergy].

In this case report, a two-year-old boy debuted with irritative and obstructive nasal symptoms and a positive house dust mite allergy test. Antihistamines and nasal steroids were prescribed, but he had persistent nasal symptoms. An initial ear-nose-throat examination was without pathology. At the age of 12 he presented with fever, headache and nasal obstruction, and an MRI scan showed a 4 × 3 × 3 cm tumour in the right ethmoid sinus. Eventually, he was diagnosed with fibrous dysplasia. Persistent nasal obstruction despite medical treatment in children with allergic rhinitis should always lead to an ear-nose-throat examination and possibly MRI scan to rule out nose and sinus tumours.