Vanishing tumefactive ANCA-associated hypertrophic pachymeningitis: A case report.

We report a case of a 59-year-old man with hypertrophic pachymeningitis (HP), initially presenting as a tumefactive lesion that disappeared spontaneously. He developed headache and left abducens nerve palsy 2 years before admission, and cerebral magnetic resonance imaging (MRI) revealed a round mass lesion. Meningioma was initially considered, but the lesion disappeared spontaneously along with the symptoms. However, 6 months before admission, left abducens nerve palsy reappeared. Repeated MRI revealed multiple intracranial tumefactive lesions. HP was diagnosed based on the pathological analysis of the biopsied specimen. HP can appear as a vanishing tumor, and pathological evaluation is essential for a precise diagnosis. If spontaneous disappearance of tumefactive intracranial lesions is encountered, the possibility of HP should be considered.