Figure 1. Myasthenia gravis (MG) is a condition involving voluntary muscles, most commonly of the eye, mouth, and throat. Normally, acetylcholine, a neurotransmitter released by a neuron, travels to the neurotransmitter receptors, leading to muscle contraction. MG is an autoimmune disease where there are fewer receptors than normal. The few existing receptors are blocked by antibodies.
The hallmark of MG is muscle weakness that increases with prolonged or repeated use. Patients often report feeling well in the morning but feel progressively weaker as the day goes on. During examination, it is critical to differentiate between fatigable weakness and nonspecific fatigue or somnolence. Objective weakness may not be obvious at the time of examination, so prompting patients to perform activities that fatigue specific muscle groups is an important element of diagnosing MG. Determining the strength in various muscles and muscle groups will help assess the severity and extent of the disease.
Patients with fluctuating fatigable muscle weakness due to MG will describe weakness of a specific group of muscles that is brought on by activity and improves with rest. In contrast, patients with generalized fatigue or exhaustion will typically describe generalized weakness, tiredness, or lack of energy, and they do not typically display true muscle weakness with provocative maneuvers. However, obstructive sleep apnea can co-occur in patients with MG; therefore, somnolence secondary to a sleep disorder may coexist with MG.
Patients with MG typically do not have primary complaints of muscle pain.
Learn more about the clinical history of patients with MG.
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Cite this: Richard Nowak. Fast Five Quiz: Myasthenia Gravis Signs and Symptoms - Medscape - Jul 08, 2021.
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