The hallmark of myasthenia gravis is muscle weakness that worsens with activity and improves with rest. Commonly affected muscles include those that control eye movement and eyelids, facial expressions, chewing, swallowing, and sometimes breathing. Early symptoms often involve drooping eyelids (ptosis) and double vision (diplopia). As the disease progresses, other muscles may be affected, potentially leading to difficulties in speaking, walking, or even breathing—known as a myasthenic crisis, a medical emergency.

The exact cause of the autoimmune response in myasthenia gravis is unknown, though it’s often associated with abnormalities in the thymus gland, which may be enlarged or contain tumors (thymomas). It can affect people of any age but is more commonly diagnosed in women under 40 and men over 60.

Diagnosis typically includes blood tests for antibodies, electromyography (EMG), and imaging studies like CT or MRI to examine the thymus gland. A common bedside test is the ice pack test, which may temporarily improve eyelid drooping.