Who Gets MG?

It is difficult to determine how many people actually have MG because the disease is often undiagnosed or misdiagnosed. However, it’s estimated that there are two to seven people in every 10,000 that have myasthenia gravis (Muscular Dystrophy Association, "Facts About Myasthenia Gravis", May 2006). MG occurs in all ethnic groups throughout the world, and in both genders. According to the National Institute of Neurological Disorders and Stroke, it most commonly affects women under age 40, and men over age 60, but it can occur at any age.

MG is not thought to be directly inherited. It is not contagious. Myasthenia gravis is more common in families with other autoimmune diseases. Sometimes the disease may occur in more than one member of the same family.

If a woman with MG becomes pregnant, sometimes the baby acquires antibodies from the mother and has MG symptoms for a few weeks or months after birth. This is called neonatal myasthenia, and the symptoms can be treated. In very rare cases, a form of myasthenia can be caused by a defective gene and appears in infants born to non-myasthenic mothers. This form of myasthenia is called congenital myasthenic syndrome; it involves problems with the ACh receptors, not the immune system.