Abstract
BACKGROUND: Herein, we detail our experience with a unique patient with concomitant multiple sclerosis (MS) and idiopathic thrombocytopenic purpura (ITP) treated with ofatumumab, which resulted in stable disease activity and platelet count normalization. CASE PRESENTATION: A 21-year-old Japanese woman presented with medial longitudinal fasciculus syndrome and was subsequently diagnosed with MS. She was treated with methylprednisolone pulse therapy (1,000 mg/day for 5 days). During her first hospitalization, her platelet count was low (40 × 10(9)/L). Based on investigations, serologic findings, and bone marrow aspiration, she was diagnosed with ITP. Following methylprednisolone treatment, oral prednisolone was initiated and gradually tapered. Glatiramer acetate was used as a disease-modifying drug (DMD). As prednisolone was tapered off, the platelet count decreased correspondingly. The clinical course included two MS relapses, each of which was treated with a methylprednisolone pulse and DMD adjustments (the DMT was sequentially switched from glatiramer acetate to dimethyl fumarate, then fingolimod, and finally natalizumab). Despite an initial recovery of the platelet count following these interventions, the platelet count declined correspondingly with the prednisolone dose reduction. Finally, the DMD was switched to ofatumumab, an anti-CD20 monoclonal antibody with pharmacological similarities to rituximab, a second-line treatment for ITP. After the initiation of ofatumumab, the patient remained clinically stable with no further MS relapses, and her platelet count stabilized over 2 years. CONCLUSIONS: Herein, we report our experience with a novel case of MS concomitant with ITP that was safely treated with ofatumumab. Considering the pharmacological similarities of ofatumumab to rituximab (a second-line treatment for ITP), anti-CD20 monoclonal antibodies such as ofatumumab could be a promising treatment option for cases of MS concomitant with ITP.