Myasthenia gravis is an autoimmune disease which results from antibodies that block or destroy nicotinic acetylcholine receptors at the junction between the nerve and muscle. This prevents nerve impulses from triggering muscle contractions. Most cases due to IgG1 or IgG3 antibodies. That attack acetylcholine receptors in the post synaptic membrane, causing complement mediated damage and muscle weakness. It is long term neuromuscular disease that leads to varying degrees of skeletal muscle weakness. In myasthenia gravis upper extremities weakness is more common than lower extremities. Involve proximal muscle than distal. In this disorder involve neck muscles, neck flexion weaker than neck extension.
Muscles are most commonly affected muscles are those of the eyes, face or swallowing. It can result in double vision, drooping eyelids, trouble talking or trouble walking. Rarely, an inherited genetic defect in the neuromuscular junction results in a similar condition known as congenital myasthenia. In pregnant women, myasthenia gravis usually occurs in 1st trimester of pregnancy. About 10-20% infants with mothers affected by the condition are born with transient neonatal myasthenia, which generally produces feeding or respiratory difficulties that develop about 12 hours to several days after birth. Juvenile myasthenia gravis is most common in females. Myasthenia gravis difficult to diagnose, as the symptoms can be subtle or hard to distinguish from both normal variants and other neurological disorders.