Congenital Myasthenic Syndrome Vs Myasthenia Gravis

Congenital myasthenic syndrome vs myasthenia gravis: What's the difference?

Let's explore congenital myasthenic syndrome vs myasthenia gravis, but first, let's understand congenital myasthenic syndrome.

Congenital myasthenic syndrome is a set of different neuromuscular conditions characterized by muscle weakness that becomes worse after physical effort. The characteristic droopy eyelids are a distinctive symptom of this condition. This disorder usually surfaces early in childhood but can develop later as well.

Affects of congenital myasthenic

This disorder primarily affects the facial muscles, ranging from the muscles in the eyelids to the muscles used for chewing, although any muscle or group of skeletal muscles can be affected. The impact of this disorder can vary greatly from person to person, ranging from mild to severe. When this condition occurs during infancy, it can affect everything from feeding to motor skills, like walking and crawling.

3 categories of condition

CMS is a blanket term that covers several different neuromuscular disorders. These conditions are grouped into three categories based on the part of the neuromuscular junction that’s affected. There are conditions distinguished by problems that affect the presynaptic (nerve cell). Just as there are conditions caused by problems in the postsynaptic (muscle cell) or the synaptic area which is the space in between the two. Yet all three of these disorders fall under congenital myasthenic syndrome.

People afflicted with this disorder are usually the offspring of both a mother and a father that have the unexpressed gene for this disorder. However, this condition can develop even if only one parent has the gene. In fact, heredity is not the only way that this disorder is expressed.

Mutations in the genes can create this condition, even if there is no history of this problem in the family. This disorder is diagnosed through a variety of different genetic tests. CMS, by definition is a form of muscular dystrophy.

Myasthenia Gravis

Myasthenia gravis is a chronic autoimmune neuromuscular disease that causes intense weakness in the muscles. It occurs when normal communication between the nerves and muscles fails to take place, resulting in antibodies blocking, altering, or destroying the receptors. This, in turn, prevents the muscles from contracting. In essence, the body turns on itself. This process can affect all the muscles in the body from the eyes to those used for breathing and moving different parts of the body, as well as the arms and the legs.

The title, myasthenia gravis, has both Latin and Greek origins and means grave, or serious, muscle weakness. This disorder becomes worse after prolonged periods of activity and subsides after rest. In fact, some symptoms can become so severe that some people are unable to walk. Normal immune functions like a fever or infection may even trigger periods of difficulty with breathing for some individuals who suffer from this condition. Those afflicted may even develop sleep apnea. Unfortunately, there is currently no cure for this disorder.

Similarities & Distinct Differences

Although congenital myasthenic syndrome and myasthenia gravis are both neuromuscular disorders, there are some distinguishing differences between the two. The major difference between these two disorders is their origin and cause. Myasthenia gravis is an autoimmune disorder, while congenital myasthenic syndrome is an inherited disease caused by defective genes. Furthermore, there are three different types of CMS, grouped into categories based on the area of the neuromuscular junction that’s affected. They are as follows: the nerve cell, the muscle cell, or the synaptic space in between the two.

Congenital myasthenic syndrome is a largely genetic disorder which often develops at birth or shortly thereafter, which explains why the word congenital is part of its title. However, if it does develop later in life, the symptoms are generally much milder. Myasthenia gravis on the other hand is caused by autoimmunity. Although both disorders affect the muscles heavily, the causes and origins are markedly different, clearly distinguishing the two.

Overall, CMS and MG are both neuromuscular disorders that impact the function of muscles heavily. The main difference is that MG is a disorder that originates from an autoimmunity, whereas CMS is a predominately genetic disorder whose onset is mostly congenital. However, genetic tests are used to diagnose both of these disorders. Ultimately, although there are many similarities, the differences are strikingly distinctive.

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Last Reviewed:
September 08, 2017
Last Updated:
October 04, 2017