A 23-year-old man was referred to our Emergency Department due to an acute-onset hemoptysis and the associated bilateral swelling of all of his major salivary glands. The elevated levels of systemic inflammatory markers with hypereosinophilia and the concurrent presence of multiple lung infiltrates made it difficult to perform a differential diagnosis, as these symptoms can also be indicative of infectious, autoimmune or hematologic disorders. A histological examination of the patient's left submandibular gland revealed strong clues as to the final diagnosis of eosinophilic granulomatosis with polyangiitis with an atypical clinical presentation, thus allowing for the administration of early and successful conservative therapy. The outcome of our case suggests that systemic vasculitis represents a rare but possible cause of acute bilateral sialadenitis in young patients.