Alemtuzumab is a monoclonal antibody that targets the CD52 protein expressed on T and B lymphocytes. This treatment may result in severe adverse events such as allergic reactions, de novo autoimmune diseases, opportunistic infections, and stroke. In this report, we described a relapsing-remitting multiple sclerosis (RRMS) patient without any risk factors for cerebrovascular disease who had a hemorrhagic stroke during the second course of alemtuzumab treatment.

Herein, we report a 52-years-old female patient with RRMS that was diagnosed 30 years ago. During the long course of the disease, she received interferons, azathioprine, fingolimod, and natalizumab. Her treatment was switched to alemtuzumab one year ago due to the inefficacy of natalizumab. The patient experienced no severe side effects except headache and nausea during the first course of the treatment, and her clinical course was stable for one year. Her EDSS was 5.0 when she was admitted for administration of the second course of alemtuzumab. On the third day of treatment, she complained of headache and hypertension (170/100) that was treated with analgesics and ramipril 2,5 mg. Four hours after infusion of the third dose, the patient had an acute loss of consciousness and left hemiplegia. Her brain computed tomography revealed a massive (66x44 mm) right putaminal hemorrhage. The patient underwent an urgent hematoma evacuation craniotomy with external ventricular drainage. One day after the surgery, the patient developed another hematoma in the left putamen when she was normotensive without apparent hematological abnormalities.

To date, only five cases with intracerebral hemorrhage associated with alemtuzumab treatment were reported. Previous reports blamed elevated blood pressure as a possible culprit in the cerebral hemorrhage. The occurrence of secondary putaminal hemorrhage when the patient was normotensive contradicts this hypothesis. This case reveals the need for further investigation of possible endothelial damage due to alemtuzumab treatment.