From the Guidelines
Patients with Anti-MuSK antibody positive Myasthenia Gravis should be treated with corticosteroids as the first line of treatment, as approximately 66% to 85% of patients show a positive response to this therapy. The use of pyridostigmine bromide, although commonly used in myasthenia gravis, may not be as effective in patients with strabismus-associated myasthenia, with about half of patients showing minimal response 1. Corticosteroids, on the other hand, have been shown to be effective in a significant proportion of patients. In some cases, immunosuppressive therapy with azathioprine or other agents such as efgartigimod alfa-fcab may be considered, although the latter is currently only FDA approved for patients who test positive for the anti-acetylcholine receptor 1. Some key points to consider in the treatment of Anti-MuSK antibody positive Myasthenia Gravis include:
- The use of corticosteroids as the first line of treatment
- The potential need for immunosuppressive therapy in some cases
- The importance of careful consideration when using anesthetic agents due to the risk of associated weakness of the respiratory muscles
- The possibility of thymectomy in certain cases, particularly in the presence of thymoma
- The potential for remission or stabilization of the disease after 2 to 3 years of treatment, at which point surgical intervention for strabismus may be considered if desired or if prism use is insufficient 1.
From the Research
Treatment Overview
The treatment for Anti-MuSK (Muscle Specific Kinase) antibody positive Myasthenia Gravis (MG) aims to reduce weakness as quickly as possible, especially in patients with bulbar or respiratory weakness. The primary goal is to achieve the minimum effective dose of medications to control the disease.
Initial Treatment
- An initial trial of acetylcholinesterase inhibitors (ACEi) is reasonable due to their benign nature and potential for rapid response, although the response is usually poor and the likelihood of side effects is relatively high 2.
- Corticosteroid treatment, starting at a dose of 1.5-2 mg/kg/day of prednisone, is recommended for all MMG patients, unless clearly contraindicated by other medical conditions 2.
Immunotherapy
- A steroid-sparing agent such as azathioprine, mycophenolate mofetil, or cyclosporine may be added to the treatment regimen 2, 3.
- Rituximab has shown promising results in MMG and should be considered in severe and refractory cases or in situations where other options are contraindicated or not tolerated by patients 2, 3.
- Efgartigimod has demonstrated good therapeutic effects in MuSK-Ab-positive MG patients, including those in exacerbation, and can be used as a rescue treatment during exacerbations and as an adjunctive therapy in the context of long-term immunotherapy 4.
Plasma Exchange and IVIg
- Plasma exchange is a effective treatment for acute exacerbations of MMG, and most reports indicate it is superior to IVIg 2, 3.
- IVIg may still be used, especially in patients who do not respond to plasma exchange or have contraindications to it 5, 3.