Management

Despite advances in the treatment of MG, there is only a small evidence base. The following treatment modalities are available:

Acetylcholinesterase inhibitors

These drugs increase the availability of the acetylcholine to act on the AChRs.

They are usually the initial drugs used in treating MG; however, they do not modify the course of the disease and provide only symptomatic benefit.

Pyridostigmine is the most frequently used drug.

Corticosteroids

These are needed to treat MG of moderate or greater severity and in mild disease that fails to respond fully to acetylcholinesterase inhibitors.

Oral prednisolone, usually started at a low dose on an alternate-day regimen, and gradually increased, is the recommended first choice short-term immunosuppressant [1,15]

Immunosuppressants

Because of the serious side effects associated with long-term steroid therapy, other immunosuppressant drugs are used as ‘steroid-sparing agents’.

Azathioprine, cyclophosphamide, cyclosporine, methotrexate and mycophenolate mofetil have been used in treating MG.

Azathioprine is the first choice in this class of drugs.

We still lack good randomised controlled trial data on longer-term efficacy, steroid-sparing effect and safety of immunosuppressants in MG [16].

There is no data from randomised controlled trials (RCT) on the impact of any form of treatment on the risk of progression from ocular to generalised MG [20].

Plasmapheresis

Plasmapheresis produces rapid, but temporary, improvement by reducing the amount of AChR antibodies. Indications are:

• MC
• Severe MG before thymectomy
• Early postoperative period
• Symptom worsening during tapering or initiation of immunosuppressive therapy

No adequate RCTs have been performed to determine whether plasma exchange improves short- or long-term outcome of MG. However, many case series studies report short-term benefit from plasma exchange in MG, especially in MC [21].

Intravenous immunoglobulins (IVIG)

The IVIG mechanism of action remains unknown.

IVIG has the same indications as plasmapheresis. However, in contrast to plasmapheresis, it does not require expensive equipment or a large bore vascular access.

Plasmapheresis usually works quicker than IVIG.

Direct comparison of the two therapies shows them to be equally effective [2,7,10,16-17].

Learning bite

Both plasmapheresis and intravenous immunoglobulin administration have been demonstrated in many case series to provide short-term benefit.

Thymectomy

There are two different indications for thymectomy in MG:

First, thymectomy for thymic tumours associated with around 10% of patients with MG [2,4].

Second, thymectomy for the treatment of MG in the absence of thymoma. It is generally agreed that patients with generalised MG between the ages of adolescence and 60 years should be offered thymectomy as 80%-85% of patients eventually experience improvement in their MG after thymectomy [2]. The precise role of the thymus in MG is still not determined nor is it clear why a minority of patients derive no benefit from the procedure [2,4].

Thymectomy is not effective in anti-MuSK-positive MG