What is gMG?
Generalized myasthenia gravis (gMG) is the most common form of myasthenia gravis (MG), a rare
autoimmune
neuromuscular disease that interrupts the communication between the nerves and muscles, causing muscle weakness and tiredness.
Symptoms & impact on daily life
Each person experiences gMG differently.
gMG is sometimes called a “snowflake disease” because symptoms can vary from person to person.
Common symptoms include:
Muscle fatigue
Trouble breathing
Trouble swallowing
Muscle weakness in areas such as arms, hands, legs, or feet
Trouble speaking
Changes in vision
How gMG affects the body
gMG interrupts signals between your nerves and muscles.
AChR=acetylcholine receptor; MuSK=muscle-specific tyrosine kinase.
The illustration above shows the area where your nerves and muscles meet, also known as the
neuromuscular junction
. This is the critical connection point where your nerves send signals to your muscles.In a healthy individual, nerves send a messenger (neurotransmitter) called acetylcholine that acts as a signal for the muscle.
In a healthy individual, nerves send a messenger (neurotransmitter) called acetylcholine that acts as a signal for the muscle.
Acetylcholine attaches to a
receptor
on the muscle surface called the acetylcholine receptor (AChR), which helps tell the muscles to move. Other receptors, including muscle-specific tyrosine kinase (MuSK), also help the muscles receive the message.In gMG, the body can sometimes mistakenly make harmful immunoglobulin G (IgG) antibodies that target these receptors on the muscle surface, also known as harmful anti-AChR and anti-MuSK antibodies.
When harmful IgG antibodies target these receptors, they interrupt the signal between your nerves and muscles. This makes it harder for your nerves to tell your muscles to move.
AChR=acetylcholine receptor; MuSK=muscle-specific tyrosine kinase.
The illustration above shows the area where your nerves and muscles meet, also known as the
neuromuscular junction
. This is the critical connection point where your nerves send signals to your muscles.What are harmful anti-AChR and anti-MuSK antibodies?
In gMG, sometimes harmful anti-AChR and anti-MuSK antibodies can be formed against the AChR and MuSK muscle receptors that are important for relaying messages from nerves to muscles.
anti-AChR
Anti-acetylcholine receptor
People with harmful antibodies that target AChR have anti-AChR antibody-positive gMG.
Found in ~80% of people with gMG
anti-MuSK
Anti-muscle-specific tyrosine kinase
People with harmful antibodies that target MuSK have anti-MuSK antibody-positive gMG.
Found in ~6% of people with gMG
Neonatal fragment crystallizable receptor (FcRn) is
a protein found naturally in your body
FcRn helps keep IgG antibodies—including harmful IgG antibodies—in your body longer.
Normally, the purpose of IgG antibodies is to help defend your body against infection and disease that can be caused by foreign proteins such as viruses and bacteria.
FcRn extends the time IgG
antibodies are in your body. This is meant to help protect your body from those foreign proteins that can cause illness.
In gMG, the body can mistakenly
make harmful IgG antibodies—such as harmful anti-AChR and anti-MuSK
antibodies—that interfere with the signal between your nerves and muscles. FcRn can also help keep harmful IgG antibodies in your body longer. This allows them to continue to disrupt the signals between your nerves and muscles.
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