Myasthenia Gravis

Myasthenia gravis is a chronic neuromuscular, autoimmune disorder that causes varying degrees of weakness involving the voluntary muscles of the body. The definition of myasthenia gravis is "grave muscle weakness".2

Myasthenia gravis may affect any voluntary muscle but most commonly affects those that control eye movements, eyelids, chewing, swallowing, coughing and facial expression. Muscles that control breathing and movements of the arms and legs may also be affected.2

At present, the cause of myasthenia gravis is unknown and as yet there is no cure. Researchers, scientists and clinicians who investigate and study the disease have gained a much better understanding of myasthenia gravis during the past 20 years. The diagnosis and practical management of myasthenia gravis are well defined and usually successful. 2,4

Recently, myasthenia gravis has been divided into the following general classifications based on clinical features and severity of symptoms of the disease:

Class I
Any ocular (eye) muscle weakness. May have weakness of eye closure. All other muscle strength is normal.
Class II
Mild weakness affecting other than ocular muscles. May also have ocular muscle weakness of any severity.
Class III
Moderate weakness affecting other than ocular muscles. May also have ocular muscle weakness of any severity.
Class IV
Severe weakness affecting other than ocular muscles. May also have ocular muscle weakness of any severity.
Class V
Defined by intubation, with or without mechanical ventilation, except when employed during routine postoperative management.

Note: For a more complete description of Classes and Subclasses, please visit the Myasthenia Gravis Foundation of America website at www.myasthenia.org DISCLAIMER: This website contains links that are not controlled by Valeant Pharmaceuticals International. Valeant Pharmaceuticals International assumes no responsibility or liability for the views, content or accuracy of this information, nor does it endorse any products that may be advertised or noted on these websites.

Subgroups/types of myasthenia gravis:

NONIMMUNE
Congenital (existing at birth) myasthenic syndrome Defects in proteins at the neuromuscular junction

IMMUNE
Neonatal myasthenia gravis Transplacental passage of AChR antibodies
Juvenile myasthenia gravis Onset before 18 years of age
Early-onset myasthenia gravis Onset from 18 to 50 years of age
Late-onset myasthenia gravis Onset after 50 years of age
Seronegative myasthenia gravis No detectable AChR antibodies5