We conducted a retrospective single-center study to describe the clinical features of sinonasal sarcoidosis (SNS) and to determine whether SNS is associated with a particular clinical phenotype of sarcoidosis. Twenty patients with histologically proven SNS (men/women, 7/13; mean age, 32 +/- 9 yr) were compared with control patients with sarcoid but without sinonasal (SN) involvement. Each patient was matched with 2 controls for the date of admittance in our institution. SN involvement occurred in the course of previously known sarcoidosis in 8 patients, whereas it preceded disease diagnosis in 12 patients. Among these 12 patients, 4 initially presented with strictly isolated SNS and 8 had other associated signs related to sarcoidosis. The most common symptoms were stuffiness (90%), anosmia (70%), and rhinorrhea (70%). Lupus pernio was frequent (50%). Local examination was constantly abnormal and showed hypertrophy (75%) and purplish coloring of the nasal mucosa with granulations (50%) on the septum and/or inferior turbinates. Computed tomography scans showed medial lytic lesions, mainly of the septum and/or the turbinates in about half the cases. All patients had negative antineutrophil cytoplasmic antibodies. Patients with SNS had significantly more frequent and severe involvement of vital organs than controls, had a longer history of sarcoidosis, and required systemic treatment more frequently (100% vs. 57.7%, p < 0.001) and for a longer time (78 +/- 42 mo vs. 29 +/- 18 mo, p < 0.0001). Corticosteroids maintenance dosage was high (10.5 +/- 6 mg daily) and mainly depended on SN involvement. Although rare, SN involvement is a severe and recalcitrant manifestation of sarcoidosis representing a therapeutic challenge.