Myasthenia gravis is an autoimmune
disorder that causes muscle weakness. An autoimmune disorder is one
in which the body produces antibodies against its own tissues.
What is going on in the body?
For unknown reasons, myasthenia gravis causes a person's immune system to
produce antibodies that attack the muscles in his or her body. The antibodies
destroy the part of the muscle that receives signals from the nerves. When a
muscle is used a great deal, it may not work properly. After a period of rest,
the muscle generally improves.
What are the causes and risks of the disease?
No one knows why a person with myasthenia gravis produces antibodies that
attack the muscles. This disorder occurs more often in women than in men. It
usually starts in women during their childbearing years. In men, the disease
most often starts in middle age. Rarely, a child may be born with myasthenia
gravis from a genetic defect.
New research findings suggest that autoimmune disorders
may be set off by a transfer of cells between the fetus and the mother during
pregnancy. The study
involved women with
scleroderma, an autoimmune disorder that affects the skin. These
women have more fetal cells in their blood even decades after a pregnancy than
women who don't have scleroderma. While further research is needed to confirm
these findings, the study does offer an explanation for the much higher
incidence of autoimmune disorders in women than in men.
Symptoms can be worsened by a number of factors, such as:
certain medicines, such as those used to treat muscle spasms, seizures, or infection
excessive cold or heat
hyperthyroidism, which cause
abnormal levels of thyroid hormone
infections, such as
or a tooth abscess
potassium in the diet