Myasthenia Gravis: Overview and Treatment

Myasthenia gravis is an autoimmune disorder involving the thymus gland that produces anti-receptor antibodies against the α1 subunit of nicotinic receptors.

It prevents acetylcholine interaction with the receptor at the neuromuscular junction, inhibiting impulse transmission. This leads to chronic, progressive weakness of skeletal muscles.

The antibodies can act by blocking the acetylcholine binding site, or cross-link the receptors to stimulate their internalization or induce postsynaptic membrane lysis to reduce the receptor functioning.

Patients with myasthenia initially display ptosis and diplopia. Later, they experience dysarthria that progresses to dysphagia. Eventually, the limbs and respiratory muscles are also affected.

Administration of anticholinesterases allows acetylcholine accumulation and muscle depolarization, leading to muscle strength improvement.

Alternative treatments include plasmapheresis to remove the circulating antibodies and administration of corticosteroids or immunosuppressants to limit the production of antibodies.

As the disorder is often accompanied by a thymus gland tumor, thymectomy shows gradual improvement of motor symptoms.