Myasthenia gravis is a chronic condition characterised by muscle fatigue and weakness that is worse on exercise and towards then end of the day. However, with treatment, most people with MG can lead normal lives.
What is myasthenia gravis?
Myasthenia gravis (MG) is an autoimmune condition where the immune system produces antibodies to structures, called receptors, on the muscle membrane adjacent to a nerve ending. Activation of these receptors causes muscle fibre contraction, and blocking some of the receptors by antibodies reduces the likelihood of an efficient contraction. This means that when a nerve signal asks a muscle fibre to contract, it is less likely to respond, muscle contraction becomes weaker and muscles tire with use (but often recover with rest).
MG is a rare condition, but it has become more commonly recognised over recent years as diagnostic tests have improved.
It can affect anyone, though it’s more common in younger women or older men.
Symptoms
The main symptoms of MG are muscle weakness and fatigue that become worse with activity and improve with rest. The symptoms are often worse later in the day than in the morning. Early symptoms usually include drooping eyelids, double vision, a change in voice or difficulty swallowing which often becomes worse during a meal . Weakness can also affect the arms, legs, and neck, and, in more severe cases, the muscles used for breathing.
Diagnosis
Suspicion of a diagnosis of MG is based upon the symptoms and signs of muscle weakness. Once suspected, investigation usually involves a blood test to look for specific antibodies. If the most common antibody present in MG (one against the acetylcholine receptor at the nerve-muscle junction, or synapse) is found, a CT scan of the chest would be the next step, as MG is linked, in a few people, to a growth in the thymus gland, a gland that lies in the chest just behind the breast bone. If this growth is present, it is usually removed, especially in younger patients.
Some people test negative for the acetylcholine receptor antibody but have a different antibody detectable by blood testing. Occasionally, nerve-conduction tests are needed to confirm the diagnosis.
Treatment
Treatment depends upon how MG affects the individual and often involves more than one form of treatment:
• Pyridostigmine, which slows the breakdown of acetylcholine released by nerve signals and increases the stimulation of muscles is often the first treatment tried
• Prednisolone, which has the effect of dampening the immune system and reducing antibodies, is often started along with the pyridostigmine, but might be held in reserve in some cases
• If there is a growth in the thymus gland, surgical removal of the gland can improve symptoms over time.
• Recently introduced newer injectable treatments can help when MG doesn’t respond well enough to the standard options
• In severe flare-ups of MG, blood plasma filtration or partial replacement can remove antibodies and control the effects of MG quickly
When to seek emergency help
Occasionally, MG can deteriorate suddenly and severely enough to affect breathing or swallowing. This is called a myasthenic crisis and is a medical emergency. If someone with MG develops sudden breathing difficulties, severe difficulty swallowing, or a rapid worsening of weakness, call for emergency medical help immediately.
Living with MG
Many people with MG lead full, active lives on treatment. Of course, treatment has to be adjusted for each person depending upon response. Pacing activity and planning demanding tasks for times of day when you typically feel stronger can all help.
If you are to start new medication, have an operation, or have developed an infection, let your doctor know that you have myasthenia gravis.