Myasthenia Gravis
An autoimmune condition where antibodies block the signal from nerves to muscles. Muscles tire with use and recover with rest, so droopy eyelids, double vision or weakness get worse as the day goes on.
Quick answer: Myasthenia gravis is an autoimmune condition that blocks signals from nerves to muscles, causing weakness that worsens with use and improves with rest. Droopy eyelids and double vision are often first. It’s diagnosed with antibody blood tests and nerve studies. Pyridostigmine, steroids, other immune treatments and sometimes thymus surgery control it for most people.
How common. About 15 to 25 people in 100,000, or roughly 1 in 5,000. It has two peaks: women in their 20s and 30s, and men over 60. It isn’t inherited and isn’t contagious.
Causes. Antibodies attack the receptor that receives the nerve’s chemical signal (acetylcholine) at the junction with the muscle. About 85 in 100 people with widespread weakness have acetylcholine receptor (AChR) antibodies; a smaller group has MuSK or LRP4 antibodies, and some have none detectable. The thymus gland is often involved, and about 1 in 10 people has a thymus tumour (thymoma).
Symptoms. Weakness that fluctuates, worsens with use or later in the day, and improves with rest. Droopy eyelids (ptosis) and double vision are the first sign in more than half. Others: slurred or nasal speech, trouble chewing or swallowing, a weak neck, and tired arms and legs. Sensation and pain aren’t affected. In about half of people who start with eye-only symptoms, weakness spreads within 2 years.
Triggers. Infection, surgery, stress, heat, pregnancy and some medicines can make it worse, including some antibiotics (aminoglycosides, fluoroquinolones and macrolides), magnesium given by drip, beta-blockers and botulinum toxin. Always tell doctors and pharmacists you have MG.
How it’s diagnosed. From the pattern of weakness on examination plus antibody blood tests (AChR, then MuSK if negative). Nerve studies (repetitive nerve stimulation or single-fibre EMG) help when antibodies are negative. A simple ice pack test over a drooping eyelid can help at the bedside. A CT or MRI of the chest looks for a thymoma. Thyroid tests are checked too, as thyroid disease is commoner with MG.
Treatment
Most people get good control. Treatment is guided by a neurologist, following the international consensus guidance (2020 update).
- Step 1 · PrescriptionPyridostigmineBoosts the nerve signal at the muscle. Taken several times a day; works within about 30 minutes.
- Works
- Improves symptoms in most people; often enough for mild or eye-only MG
- Access
- PBS-subsidised
- Watch for
- Tummy cramps, diarrhoea, sweating and extra saliva.
- Step 2 · PrescriptionPrednisolone (a corticosteroid)Started low and increased slowly, because a fast start can briefly worsen weakness.
- Works
- Improves weakness in most people within weeks
- Access
- PBS-subsidised
- Watch for
- Weight gain, mood change, high blood sugar and bone thinning; the aim is the lowest dose that works.
- Step 3 · SpecialistSteroid-sparing immune treatmentsAzathioprine is used most; mycophenolate, methotrexate or tacrolimus are alternatives.
- Works
- Let people lower steroids; take 6 to 18 months to work fully
- Access
- Specialist-guided
- Watch for
- Regular blood tests for blood counts and liver.
- Step 4 · SurgeryThymectomy (removing the thymus)Recommended for any thymoma, and considered for people aged 18 to 65 with generalised AChR-antibody MG.
- Works
- In the MGTX trial, people who had thymectomy had milder weakness and needed less prednisone over 3 years
- Access
- Public or private surgery
- Watch for
- Benefits build over months to years.
- Step 5 · SpecialistNewer and rescue treatmentsImmunoglobulin (IVIg) or plasma exchange for crises or before surgery. Newer targeted medicines, such as complement inhibitors (eculizumab, ravulizumab, zilucoplan) and FcRn blockers (efgartigimod, rozanolixizumab), for hard-to-treat MG.
- Works
- IVIg and plasma exchange work within days; newer medicines improved daily function in trials
- Access
- Hospital or specialist only; access varies
- Watch for
- Meningococcal vaccination is needed before complement inhibitors.
Living with it
- Plan demanding tasks for when you’re strongest, often the morning, and rest between.
- Carry a list of your medicines and an MG alert card or bracelet.
- Check new medicines with your pharmacist or neurologist first.
- Keep vaccinations up to date (ask which are safe with your treatment) and treat infections early.
- Plan pregnancy with your neurologist; babies may have brief weakness after birth.
See your GP if
- Your eyelid droops or you see double, especially later in the day
- You’re weak in a way that gets worse with use and better with rest
- Your speech becomes slurred or nasal after talking for a while, or chewing tires you
- You have MG and symptoms are slowly getting worse
Get urgent help for breathlessness, trouble breathing when lying flat, a weak cough, or choking or being unable to swallow saliva. This can be a myasthenic crisis, which can stop breathing: call 000 (Australia) or your local emergency number.
Outlook. With modern treatment, most people with MG live a normal life span and many have few symptoms. Up to about 1 in 5 has a myasthenic crisis at some point, usually early on or with an infection, which is treatable in hospital. Myasthenia Gravis Awareness Month is in June: see our health days calendar. In Australia, Rare Voices Australia supports the nearly 2 million Australians living with a rare disease.
Common questions
What are the first signs of myasthenia gravis?
Usually a drooping eyelid or double vision that’s worse when tired or later in the day. Some people first notice slurred speech, trouble chewing or swallowing, or weak arms.
Is myasthenia gravis serious?
It can be, as weakness of breathing and swallowing muscles is dangerous. But with treatment most people do well and live a normal life span.
What medications should be avoided with myasthenia gravis?
Some antibiotics (aminoglycosides, fluoroquinolones such as ciprofloxacin, and macrolides such as azithromycin), magnesium by drip, beta-blockers and botulinum toxin can worsen it. Always check new medicines with your doctor or pharmacist.
Is myasthenia gravis hereditary?
No, it’s an autoimmune condition, not inherited. A rare group of conditions called congenital myasthenic syndromes is genetic, but that’s different.
Can myasthenia gravis go into remission?
Yes. Many people reach minimal or no symptoms with treatment, and some can reduce or stop medicines over time, especially after thymectomy.
What blood test is used for myasthenia gravis?
Acetylcholine receptor (AChR) antibodies first, then MuSK and sometimes LRP4 antibodies if negative. About 1 in 10 people has none detectable.
Is myasthenia gravis a neurological disease?
Yes. It affects the junction between nerves and muscles and is managed by neurologists.
Evidence and more information
- Narayanaswami et al, Neurology 2021: International consensus guidance for management of myasthenia gravis, 2020 update
- Wolfe et al, NEJM 2016: Randomized trial of thymectomy in myasthenia gravis (MGTX)
- NHS: Myasthenia gravis
maladywise.com/myasthenia-gravis/