Response to Therapy in Myasthenia Gravis with Anti‐MuSK Antibodies

Abstract

Myasthenia gravis (MG) with antibodies against the muscle-specific tyrosine kinase (MuSK abs) is often a severe disease requiring aggressive treatment. Various immunosuppressive (IS) regimens have been employed; the efficacy of plasma exchange is unanimously recognized, while the indication for thymectomy is controversial. We evaluated the response to therapy in 57 MuSK-positive patients (12 M/45 F) comparing our experience with other authors' results. Disease severity and response to treatment were graded according to MG Foundation of America; follow-up ranged from 0.5-29 years. Owing to both MG severity and the unsatisfactory response to cholinesterase inhibitors, most patients (54/57) needed IS treatment, and 35 received one or more courses of plasma exchange and intravenous immunoglobulin. At the end of follow-up, the rate of complete remission was 8.8%, and IS treatment had been withdrawn in only 10/54 patients. The extent of therapeutic response varied considerably. With conventional IS therapy (prednisone alone or in combination with azathioprine or cyclosporine), most patients achieved good control of their disease, but 30% of them were left with permanent facial and bulbar weakness. In patients with refractory disease, the use of mycophenolate mofetil and rituximab proved very effective, as also reported by other authors. In our and others' experience, MuSK-positive MG markedly improves with IS therapy, although, in comparison with the AChR-positive disease, it is characterized by a lower remission rate, as a higher proportion of patients remain dependent on treatment. Thymectomy is mostly considered scarcely effective; however, at present, no firm conclusions can be drawn on its role in the treatment of this form of MG.

The Role of MuSK in Synapse Formation and Neuromuscular Disease

“…Approximately 15% of patients with MG have autoantibodies to MuSK, although the percentage varies among different ethnic groups (Evoli et al 2008;Vincent et al 2008). Muscle weakness in anti-MuSK MG can be severe, requiring respiratory assistance.…”

Precision medicine in myasthenia graves: begin from the data precision

“…This phenomenon was found in other autoimmune disease, for example, in a proportion of multiple sclerosis patients, oligoclonal bands could become positive in repeated testing several months after the first negative testing (25); (III) effects of treatment on antibody levels. In MG, once the antibodies appear, they tend to be positive consistently even their level decrease after effective treatment with potent immunosuppressive agents or thymectomy (26)(27)(28)(29)(30). This may be related to persistence of long-lived plasma cell (31).…”

Myasthenia Gravis: New Insights into the Effect of MuSK Antibodies and Acetylcholinesterase Inhibitors

“…In this study, elderly MG patients were more prone to develop cholinergic side effects, as well as EDs. Additionally, MuSK+ MG patients often have a negative edrophonium test and are also reported to clinically benefit less from pyridostigmine bromide (Evoli, Bianchi et al 2008). Instead, MuSK+ patients may worsen or develop pronounced nicotinic side effects including muscle cramps and fasciculations in response to PB treatment (Evoli, Tonali et al 2003;Punga, Flink et al 2006).…”