Myotonia Congenita - Symptoms

Symptoms

The prolonged muscle contractions, which occur most commonly in the leg muscles in recessive mutations, and more commonly in the hands, face, and eyelids in dominant mutations, are often enhanced by cold and inactivity, and in some forms is relieved by repetitive movement known as "the warm up effect". The warm up effect often diminishes quickly with rest. Some individuals with myotonia congenita are prone to falling as a result of hasty movements or an inability to stabilize themselves after a loss of balance. During a fall, a person with myotonia congenita may experience partial or complete rigid paralysis that will quickly resolve once the event is over. However, a fall into cold water may render the person unable to move for the duration of submergence. As with myotonic goats, children are more prone to falling than adults, due to their impulsivity.

The two major types of myotonia congenita are known as Thomsen disease and Becker type myotonia congenita, the latter sometimes being called "generalized myotonia congenita". These diseases are distinguished by the severity of their symptoms and their patterns of inheritance. Becker disease usually appears later in childhood than Thomsen disease and causes more severe myotonia, muscle stiffness and pain. People with Becker disease often experience temporary attacks of muscle weakness, particularly in the arms and hands, brought on by movement after periods of rest. They may also develop mild, permanent muscle weakness over time. This muscle weakness is not seen in people with Thomsen disease. However, in recent times, as more and more of the individual mutations that cause myotonia congenita are identified, these limited disease classifications are becoming less widely used.

This disorder has high phenotype variability. Severity of symptoms can vary greatly between individuals and throughout the life of the individuals themselves. Part of this may be because there are over 80 different mutations that can cause the disorder, each with their own specifics, and also because myotonia congenita is an ion channel disorder, and ion channels are sensitive to internal and external environmental factors.

Adrenaline/epinephrine is well known to make myotonia worse in most individuals with the disorder, and a person with myotonia congenita may experience a sudden increase in difficulty with mobility in a particularly stressful situation during which adrenaline is released.

Due to the invisible nature of the disorder, the fact that those with myotonia congenita often appear very fit and able bodied, general lack of knowledge about the disorder by the general and medical community, and oftentimes by the individual themselves, and the potential for inconsistency with the symptoms, many people with myotonia congenita have experienced a degree of social persecution at one time or another because of the effects of their disorder.

Some form of myotonia congenita is estimated to affect 1 in 100,000 people worldwide.

Early symptoms in a child may include:

• Difficulty swallowing
• Gagging
• Stiff movements that improve when they are repeated
• Frequent falling

Possible complications may include:

• Aspiration pneumonia (caused by swallowing difficulties)
• Frequent choking or gagging in infants (also caused by swallowing difficulties)
• Abdominal muscle weakness
• Chronic joint problems
• Injury due to falls