Myasthenia Gravis

What is myasthenia gravis?

Myasthenia gravis (MG) is a chronic, autoimmune disorder caused by a breakdown in the communication between nerve endings and muscles in the neuromuscular junction. At the junction, the nerve ending and muscle communicate via a neurotransmitter known as acetylcholine.

In MG, antibodies block or destroy receptors at the junction, affecting signal transmission. This results in muscle fatigue and weakness.

What are the types of myasthenia gravis?

• Ocular MG: Affects only the eye muscles, causing intermittent drooping eyelids and double vision. It may remain localised to the eye muscles, or progress to generalised MG.

• Generalised MG: Involves muscles beyond the eyes, including those used for breathing, swallowing and limb movement.

• Early-onset: Before age 50, more common in females, and often linked to an enlarged thymus

• Late-onset: After age 50, more common in males

• Thymoma-associated: Linked to thymic tumours (around 10-15% of cases)

• Congenital myasthenic syndromes (CMS): Inherited, non-autoimmune form present from birth.

• Transient neonatal MG: Temporary weakness in newborns of mothers with MG, resolving after birth.

• Seronegative MG: No detectable antibodies but similar symptoms; diagnosed clinically.