In the United States, Myasthenia Gravis affects around 14 to 40 out of every 1000 individuals. The number of cases of Myasthenia Gravis has increased in recent years, corresponding to the recent surges in autoimmune conditions in the past few years.

While the condition affects individuals of all ethnicities, Myasthenia Gravis is more prevalent in females than males. In addition, the onset of symptoms for the condition occurs much earlier in females when they are in their 20s and 30s. However, males typically become aware of their symptoms in their 50s or 60s. Although it is rare, infants can sometimes develop a form of the condition, called neonatal myasthenia, which is caused due to antibodies from their mother with Myasthenia Gravis being transferred to the fetus.

Myasthenia Gravis is an autoimmune disease, where the body’s own immune cells produce antibodies which attack receptor proteins in muscles responsible for nerve impulse reception. In unaffected individuals, the neurotransmitter Acetylcholine can diffuse across the neuromuscular junction to transmit nerve impulses and trigger muscle contraction. However, in individuals with Myasthenia Gravis, antibodies block and destroy the sites that serve as receptors for the neurotransmitter Acetylcholine. Due to this, there is a decreased number of available Acetylcholine receptors for the neurotransmitter to bind and hence nerve impulses cannot effectively pass through the neuromuscular junction. Therefore, this causes weak muscle contractions, which is characteristic of Myasthenia Gravis. 

The cause of Myasthenia Gravis is currently unknown. However, given that close to 75% of affected individuals also have thymus abnormalities, some scientists have linked the condition to the thymus (a lymphoid tissue organ typically responsible for proper development of the immune system). The thymus typically removes antibodies causing autoimmune responses. Researchers have hypothesized that Myasthenia Gravis can be attributed to the thymus malfunctioning, which allows for the survival of antibodies that cause unregulated autoimmune responses.

The symptoms for Myasthenia Gravis largely depend on the area affected by the condition. For example, ocular Myasthenia Gravis affects primarily the eye muscles, so droopy eyelids (ptosis) and hence blurred vision are common symptoms. More generally, Myasthenia Gravis begins with muscle weakness around the eye, jaw, throat, and face. Due to the weakening of facial muscles, the condition can cause speech difficulties (dysarthria) or swallowing problems. Individuals can also experience weakening of arm and leg muscles and muscle atrophy can eventually occur. Individuals with the condition can also experience shortness of breath. However, the severity of the symptoms and the muscle weakness greatly varies depending on the individual and based on the amount of activity done.

Given that Myasthenia Gravis is typically accompanied by muscle weakness, it is often undiagnosed for many years in individuals with a milder form of the condition. However, the condition can be detected in a number of ways now through a multitude of different tests. Many of the tests work by detecting symptoms of the condition since the direct cause of the condition is still unknown.

Tests to diagnose Myasthenia Gravis include:

• Blood test → immunoassays can be used to determine the presence and quantity of Acetylcholine receptor antibodies. If the levels for the antibodies are unusually high, this suggests that the individual has the condition

• Electrodiagnostics → it involves repetitive nerve stimulation through electric pulses and can help detect whether there is impaired nerve-to-muscle transmission

• Physical and neurological examinations → can help doctors determine whether the individual is suffering from muscle weakness

• Diagnostic imaging → it can be used to detect the presence of a thymoma, which is a tumor that is often indicative of Myasthenia Gravis

• Pulmonary function testing → it can help measure the strength of breathing and detect shortness of breath, which could lead to myasthenic crisis (when respiration completely fails)

Myasthenia Gravis can be controlled through a number of treatments to reduce muscle weakness:

• Thymectomy → the dysfunctional thymus is removed, which can potentially help resolve some of the immune system functioning issues

• Anticholinesterase medications → reduces the breakdown of Acetylcholine in the neuromuscular junctions, which contributes to increased muscle strength

• Monoclonal antibody → treatment that targets the anti-Acetylcholine receptor antibodies that damage the neuromuscular junction

• Immunosuppressive drugs → the production of harmful autoimmune antibodies is suppressed, but these drugs can often cause adverse side effects

• Plasmapheresis and intravenous immunoglobulin → removes the harmful antibodies that are attacking the body’s own cells and floods the individual’s body with healthy antibodies. This treatment is only effective for a limited amount of time.

Treatment for Myasthenia Gravis can greatly reduce the severity of the symptoms and reduce overall muscle weakness. In certain cases, individuals can go into either temporary or complete remission and continue with a completely normal lifestyle.

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https://myasthenia.org/

https://www.hopkinsmedicine.org/health/conditions-and-diseases/myasthenia-gravis