Multiple systemic diseases produce various clinical manifestations in the sinonasal area. They usually appear as difficult-to-diagnose disease processes with slow, atypical clinical courses. The aim of this study was to evaluate the sinonasal manifestations of systemic vasculitides, highlighting key points for diagnosis and differential diagnosis with other pathological entities, especially cocaine-induced midline destructive lesions (CIMDL). A retrospective study was performed of 10 patients treated in our hospital during the last 5 years with an initial diagnosis of systemic vasculitides with sinonasal involvement: eight patients with granulomatosis with polyangiitis (GPA; new nomenclature for Wegener granulomatosis) and two patients with Churg-Strauss syndrome (CSS). The study variables were clinical presentation, nasal endoscopy results, maxillofacial scan results, nasal biopsy results, erythrocyte sedimentation rate, and autoimmune antibody levels. The definitive diagnosis was GPA in six (60%) patients, CSS in two (20%) patients, and CIMDL in two (20%) patients. Nasal symptoms were similar in all patients, but nasal polyps were present in only one patient with CSS. Systemic manifestations were absent in patients with CIMDL. Likewise, peripheral eosinophilia was observed only in the two patients with CSS. Specific positive biopsy specimens were obtained in six patients (all six patients with GPA, one with CSS, and one with CIMDL). Antineutrophil cytoplasmic antibodies (ANCA) were positive in all patients with GPA (proteinase 3 antigen in five patients and myeloperoxidase in one patient), and perinuclear ANCA was positive in one patient with CIMDL; however, this patient showed an undefined pattern. Finally, the response to treatment was adequate in all patients excluding those with CIMDL. GPA and CIMDL syndromes pose a difficult differential diagnosis because they have common clinical, serological, and histological presentations. Negative histological results do not exclude the diagnosis of sinonasal vasculitides. The absence of systemic manifestations and the lack of response to treatment will lead to the confirmation of CIMDL syndrome in a cocaine user. Otolaryngologists play an important role in the early and differential diagnosis of these diseases.