Myasthenia gravis (MG) is an autoimmune disorder where the body’s immune system responds against it by degrading the neuromuscular junctions ultimately affecting the motor activities in patients. In 1895, German neurologist and psychiatrist Friedrich Jolly coined the term "myasthenia gravis pseudoparalytica", which is now known as myasthenia gravis. It has socio-economic implications, including impaired functioning in work, self-care, independent living, and quality of life. MG can also be congenital along with development during a lifetime. This disorder is characterized by muscle weaknesses due to autoimmune reactions triggered to degrade mainly the acetylcholine receptors in patients with MG.
Patients can often experience aggravated symptoms triggered by infection, stress, or improper use of medications. The aggravated state can become severe enough to affect the respiratory muscles in patients and they may need ventilation. Such type of a condition is known as a myasthenic crisis.
The hallmark symptoms of myasthenia gravis are:
Ptosis (condition referring to upper eyelid drooping)
Diplopia (double vision)
Dysarthria (slurred speech)
Dysphagia (discomfort and difficulty in swallowing)
Dyspnea (shortness of breath)
Limb or axial fatigable weakness
The diagnosis depends on the clinical examination, the patient’s history, and physical findings such as specific distribution of muscle weakness and fatigue in a patient’s body, without impairing other nerves. The recommended investigations include neurological examination, blood tests for antibodies, ice-pack test, edrophonium test, repetitive nerve stimulation, neuromuscular jitter study, and thymus imaging.
Musk or muscle-specific kinase autoantibody and acetylcholine receptor (AChR) specific autoantibodies are the major cause of degrading synaptic junction of muscles and neurons. Additionally, the thymus gland may become enlarged by producing excess dysfunctional immune cells, causing the immune system to attack its cells and tissues and produce acetylcholine receptor antibodies in MG patients.
Both genetic and environmental factors, major predisposing factors for MG, are important causal factors. Although the association of MG with environmental risk factors is not fully elucidated, heat is known to worsen the symptoms of the disease such as fatigue. Other factors that can worsen myasthenia gravis include illness or infection, surgery, stress, certain medications such as beta-blockers, quinidine gluconate, quinidine sulfate, quinine, phenytoin, certain anesthetics, and antibiotics. Additionally, MG may be worsened during pregnancy and menstruation. Myasthenia gravis is rarely seen in infants.
There is no definite cure for myasthenia gravis; the management includes symptomatic treatment and immunosuppressive therapy. The mainstay of therapeutic intervention is the use of acetylcholinesterase inhibitors such as pyridostigmine, plasma exchange, intravenous injection of immunoglobulins, immunosuppressive drugs, monoclonal antibody therapy, and thymectomy (removal of thymus gland surgically) is used for the treatment of MG patients after diagnosis.
Several new drugs for MG treatment are under development. Most patients with MG experience limitations in leisure activities, and work and suffer from depression. Several organizations in the USA have support groups that offer counseling, care, financial services, legal advocacy, and medical and travel aid. The future treatment of myasthenia gravis relies on elucidating the molecular basis of the multi-faceted immunological response involved in MG, thus, paving the way for a targeted therapeutic strategy that will normalize the defective immune system in this disease.