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Despite the efficacy of standard immunotherapy, a subset of myasthenia gravis (MG) patients remains medically refractory. Muscle-specific kinase autoantibody positive (MuSK+) patients, in particular, do not respond well to treatment, exhibit more bulbar symptoms and have more frequent exacerbations as compared to acetylcholine receptor antibody positive (AChR+) patients.1 ,2 Autoreactive B cells are appropriate candidates for targeted drug therapy as they play an important role in the pathogenesis of MG.2–4 Rituximab, a chimeric monoclonal antibody that targets the CD20 antigen on B lymphocytes, is the only B cell–directed biologic currently approved for clinical use. Several groups, including our own, have observed the benefits of rituximab in both AChR+ and MuSK+ patients.2–7 The durability of this positive response has varied among different reports. One group reported sustained benefit after a mean follow-up of 31 months in the combined AChR+ and MuSK+ cohort and 40 months in the MuSK+ subpopulation.3
Here, we report our experience with the sustained effects of rituximab in nine refractory MuSK+ patients in a follow-up period ranging from 2 to 5.5 years.
A retrospective study was performed of generalised MuSK+ MG patients referred to our neuromuscular clinic from 2003 to 2011. Nine MuSK+ patients were identified with refractory disease and treated with rituximab. The group consisted of eight females and one male with a median age of 40. Patients were defined as refractory when they: (1) could not lower …
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