Myasthenia Gravis – Causes, symptoms, diagnosis and treatment

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Myasthenia gravis is as an autoimmune neuromuscular disease. The immune system produces antibodies that blocks muscle receptor sites, causing weaker signal transmission (neurotransmission), which leads to weakness of muscles. 

myasthenia gravisWhat is myasthenia gravis?

Myasthenia gravis is a disorder that causes symptoms like muscle weakness and rapid fatigue due to abnormal communication between nerves and muscles. Voluntary muscles like those that control eye and eyelid movement, facial expressions, chewing, talking and swallowing are often involved in the disorder. Sometimes muscles that control breathing, neck and limb movements may also get affected.

Though it can affect anybody irrespective of age and gender, it’s more common in women younger than 40 and in men older than 60. In neonates (a child less than 4 weeks old), it usually lasts only for 2-3 months. About 90 per cent of patients live a near-normal life with medical treatment.

Causes of myasthenia gravis

Myasthenia gravis is regarded as an autoimmune neuromuscular disease. The immune system produces antibodies that blocks muscle receptor sites causing weaker signal transmission (neurotransmission), which leads to weakness of muscles.

Though the exact cause of myasthenia gravis is unknown, it is supposed to be associated with thymus gland tumour, which produces antibodies responsible for myasthenia gravis. Factors like fatigue, illness, stress, heat and medications like beta blockers, calcium channel blockers, quinine, few antibodies etc. also can worsen the disorder.

Symptoms of myasthenia gravis

  • Myasthenia gravis weakens voluntary muscles and some of its symptoms are as follows:
  • May lead to altered speaking, difficulty in swallowing and problems while chewing,
  • Weakness in legs, arms and neck muscles may be seen.
  • Drooping of one or both eyelids and double vision are also symptoms.
  • Symptoms worsen with increased activity of the affected muscle and can be improved with scheduling rest for a maximum period of time.

Diagnosis of myasthenia gravis

First step towards diagnosis of myasthenia gravis is a physical examination which identifies muscle strength, reflex and sensations.

Further investigations can be done to confirm the diagnosis. These include tests such as edrophonium test, blood analysis, repetitive nerve stimulation, single-fibre electromyography (EMG) and imaging scans.

Treatment of of myasthenia gravis

Though there is no cure for myasthenia gravis, patients can undergo treatment to suppress the symptoms. Medication, surgery and lifestyle modifications can help to resolve its symptoms.

In general, medications like cholinesterase inhibitors and immunosuppressant’s can be prescribed by the doctor. Therapies like plasmapheresis and intravenous immune globulin are also recommended.

In patients with an identified thymus tumour as the cause of myasthenia gravis, the tumour can be removed by performing surgery. Surgery is not recommended if symptoms are mild, if the symptoms involve only eyes or if patient is over the age of 60.

Some lifestyle modifications that can help to improve the symptoms are:

  • Consuming soft food
  • Rest between bites is required
  • Scheduling maximum rest
  • Use of eye patch and lens prisms
  • Avoiding stress and heat exposure

Complications due to myasthenia gravis

Myasthenia gravis patients have a higher risk of developing other autoimmune disorders, such as thyrotoxicosis, rheumatoid arthritis, and systemic lupus erythematosus (lupus).

They can also develop complications like underactive or overactive thyroid and pernicious anaemia.

Prolonged myasthenia gravis can lead to a condition called myasthetnic crisis. It is a life threatening condition that weakens the muscles involved in breathing.

Photograph via Wikimedia Commons 

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