RÉSUMÉ
A lady in her 70s with a background of multiple sclerosis (MS) and late-onset asthma was admitted with a 2-week history of cough and shortness of breath, progressive right-sided weakness and functional decline. Investigation revealed eosinophilia, elevated myeloperoxidase antineutrophil cytoplasmic antibody, CT sinuses showed long-standing inflammatory changes consistent with sinonasal polyposis and MRI head showed lesions consistent with vasculitis. She then developed left-sided weakness and increased wheeze. Review of her case notes demonstrated that, the eosinophilia was long-standing, her asthma was severe and steroid-dependent, and her neurologic syndrome was atypical for MS. Intravenous methylprednisolone then cyclophosphamide were administered. She demonstrated remarkable improvement, becoming more alert, with improvement in left-sided weakness. A diagnosis of Churg-Strauss syndrome was established. She was discharged to a nursing home with outpatient rheumatology follow-up. The diagnosis of MS was revisited.