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Thursday, July 31, 2014
Diabetes and Myasthenia Gravis
If a person has diabetes and myasthenia gravis is there any way you can treat the myasthenia gravis without affecting the diabetes?
I would like to respond to this question primarily with some general principles but with a few specifics added in. Myasthenia gravis is a muscle disease caused by abnormalities in the immune system, a so-called `autoimmune disease.` The immune system forms an antibody which acts on the surface of the muscle cell to block a signalling molecule called acetylcholine usually transmits instructions for muscle action. Therefore, most treatment for myasthenia gravis is directed either towards replacing the acetylcholine or suppressing the immune response. Drugs which block acetylcholine breakdown are used. Immunosuppression is attempted either with immunosuppressant drugs; the use of an operation to remove the thymus, a major source of the aberrant immune response; or some other newer approaches.
Of these therapies, one in particular, corticosteroid drugs, most commonly prednisone or prednisolone, is likely to have a substantial negative impact on blood sugar control. It may bring out underlying diabetes that was not apparent before or it may worsen blood sugar control in a person already known to have diabetes. The decisions about choices of therapy for the myasthenia need to consider all the potential benefits and risks in a given individual. In some, the decision will be that the benefit of the prednisone on the myasthenia can`t be achieved as well or as safely with other means and it becomes necessary to accept worsening of the blood sugar control as a condition of treatment. As a diabetes specialist, I frequently take the approach of accepting that choice and making plans to make the diabetes treatment more aggressive to protect against the glucose raising effects of the treatment.
In a broader sense, control of blood sugar depends on exercising large muscles that help to dispose of carbohydrate in the diet. Some muscle disease, particularly that affecting respiratory muscles, will reduce the amount of exercise and impair the ability of other muscles to respond appropriately to a carbohydrate load. In that sense, there is a relationship between the myasthenia and diabetes itself rather than between the myasthenia drugs and diabetes and that can be hard to get around.
The bottom line is that the decisions need to be made taking the whole person into account, including other seemingly unrelated diseases and the person`s ability to take advantage of compensatory measures that may help to reduce the effect either of the disease or of its treatment.
Please feel free to write back.
Robert M Cohen, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati