Myasthenia gravis (MG) is an autoimmune disorder that impairs communication between nerve and muscle cells, resulting in muscle weakness and fatigue.
The clinical hallmark of MG is muscle weakness — usually involving specific muscle groups — which worsens with repetitive movement. Affected muscles may include those of the eyes, face, jaw, throat, arms, and legs, and even those involved in breathing (respiratory muscles).
Although the disease usually becomes evident during adulthood, the onset of symptoms may occur at any age, be sudden, and often not immediately associated with MG. The age of onset tends to be different between men and women, with men usually developing the disease later when they are in their 50s or 60s, and women developing it earlier when they are in their 20s and 30s.
Eyes and eyelids
Initially, MG tends to affect the muscles that control eye and eyelid movements, causing ocular weakness. This is seen in approximately 85% of MG patients. Consequently, a partial paralysis of eye movements, double vision (diplopia), and drooping of the upper eyelids (ptosis) are usually among the first signs and symptoms of MG.
In about 10%–40% of MG patients, symptoms are limited to eye and eyelid muscles, a form of the disease known as ocular MG. But for others, muscle weakness spreads to other parts of the body within a few years, giving rise to a more widespread and potentially severe form of the disease, called generalized MG.
Face, neck, and throat
In about 15% of MG patients, early symptoms also involve weakness of the face, neck, and throat muscles. In such cases, patients may have difficulties speaking (dysarthria), or their speech may become altered, with their voice sounding weak, hoarse, or nasal.
Patients may have difficulties swallowing (dysphagia) and choke easily, which in turn makes eating, drinking, or taking pills more difficult. In some cases, liquids may come out from the nose. Also common are eating problems due to chewing muscles tiring out halfway through a meal, particularly when consuming something hard like a steak.
Patients’ ability to make certain facial expressions may become limited as a result of weakness in the muscles that control facial expressions. For instance, a smile may look like a snarl.
Weakness in neck muscles may make it difficult for patients to hold up their head.
Limbs and other parts of the body
In generalized MG, weakness tends to spread sequentially from the face and neck to the upper limbs, hands, and then to the lower limbs. In these cases, patients may have difficulties performing several tasks, such as rising from a sitting position, lifting their arms over their head, walking long distances, climbing stairs, or gripping heavy objects.
Constant tiredness and aching muscles after physical activity can also be a sign of MG. In general, muscle weakness tends to be worse in the upper parts of the body than in the legs and feet.
When MG affects the muscles that control breathing, it can lead to a myasthenic crisis, a medical emergency that often involves hospitalization and may require the temporary use of a ventilator to assist with breathing.
Last updated: July 29, 2021
Myasthenia Gravis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.