Background.-Dural enhancement is a characteristic finding in both spontaneous intracranial hypotension and hypertrophic pachymeningitis. Positional headache is the most important feature that distinguishes the two diseases. We report a patient with granulomatosis with polyangiitis (formerly Wegener's granulomatosis) who initially manifested like spontaneous intracranial hypotension. Case presentation.-We report here the case of a 63-year old man who presented with severe positional headache. The patient had typical symptoms, symmetric dural enhancement, and a recent history of nontraumatic subdural hygroma which led to the diagnosis of spontaneous intracranial hypotension, but was finally diagnosed as granulomatosis with polyangiitis-associated secondary hypertrophic pachymeningitis. Cyclophosphamide therapy was effective for the maintenance of remission. Conclusions.-Hypertrophic pachymeningitis associated with granulomatosis with polyangiitis can present with positional headache and subdural hygroma, mimicking spontaneous intracranial hypotension. Granulomatosis with polyangiitis should be suspected when patients with spontaneous intracranial hypotension or hypertrophic pachymeningitis show atypical features.