Myasthenia Gravis Studies

by Quest Staff on July 1, 2009 - 2:12pm

QUEST Vol. 16, No. 3

A variety of studies concerning myasthenia gravis (MG), a disease in which the immune system mistakenly attacks specialized parts of the junction between nerve and muscle cells, were presented at the 61st annual meeting of the American Academy of Neurology, held in Seattle April 25-May 2, 2009.

Some studies examined alternatives to long-term, high-dose prednisone. Prednisone, a corticosteroid drug that suppresses parts of the immune system, is often prescribed for this type of MG, and is fairly effective at helping people maintain strength. However, it has many side effects, such as weight gain, high blood pressure, diabetes, bone loss and psychological problems, if taken for long periods of time at high doses.

Mycophenolate mofetil allowed decreased prednisone dose

Neuromuscular Junction
The acetylcholine receptors, which receive signals from nerve cells, are the typical targets of the immune system in MG.

Michael Hehir at the University of Virginia Health System in Charlottesville, and colleagues, found a drug called mycophenolate mofetil (CellCept), when added to prednisone or substituted for prednisone, allowed people with MG to reduce or eliminate their prednisone intake during the second and third years of their therapy. There were 103 people in this study, all of whom had the type of autoimmune MG in which the acetylcholine receptors are the target of the immune system. These receptors are on the muscle fibers and receive signals from nerve fibers.

Those treated with mycophenolate mofetil alone began to improve between six months and a year after starting the drug. In the group taking mycophenolate mofetil and prednisone, the prednisone dose decreased after a year of mycophenolate mofetil. More than two years after starting mycophenolate mofetil, 53 percent of participants were off prednisone entirely, and 74.5 percent were taking less than 7.5 milligrams per day (a low dose).

Methotrexate allowed reduction of prednisone dosage

Faisal Raja at the University of Kansas Medical Center in Kansas City, Kan., and colleagues, found that eight people with MG tolerated an immunosuppressant medication called methotrexate (Rhematrex, Trexall), and four were able to reduce their prednisone dosage after an average of 8.7 weeks after starting methotrexate.

No one experienced any methotrexate-related adverse events, but no one had an improvement in their functional scores.

In seven people, the acetylcholine receptor was the autoimmune target. In one, it was a protein called muscle-specific receptor tyrosine kinase, or MUSK, which is needed at the junction of nerve and muscle fibers.

In ocular MG, prednisone reduced symptom spread

Another study, conducted by Mark Kupersmith at Roosevelt Hospital and the New York Eye and Ear Infirmary in New York, found prednisone appeared to prevent or at least delay the onset of generalized (all over the body) MG in people who only had ocular (eye-muscle) MG. It also controlled double vision resulting from ocular MG.

Eighty-seven people with ocular MG participated in this study, of whom 55 received prednisone and 32 did not.

Participants were followed for more than four years or until generalized MG developed. Generalized MG developed in seven (13 percent) of the 55 who took prednisone and in 16 (50 percent) of the 32 who did not. It typically appeared within a year in those not taking prednisone.

Double vision associated with ocular MG was present at the end of the study in 15 participants (27 percent) of the 55 who took prednisone and in 18 (57 percent) of the 32 who did not.

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