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 inactivity, and in some forms are relieved by repetitive movement known as "the warm-up effect". This effect often diminishes quickly with rest. Some individuals with<unk>  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<unk>  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<unk>  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 transient weakness. Although myotonia in itself is not normally associated with pain, cramps or myalgia may develop. 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 observed in people with Thomsen disease. However, in recent times, as more of the individual mutations that cause<unk>  are identified, these limited disease classifications are becoming less widely used. Early symptoms in a child may include: * Difficulty swallowing * Gagging * Stiff movements that improve when they are repeated * Frequent falling * Difficulties opening eyelids after strenuous contraction or crying (von Graefe's sign) 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 Phenotypic variability Both Thomsen and Becker myotonia have high phenotype variability. Severity of symptoms can vary greatly between individuals and throughout the lives of the individuals themselves. This may be partly because there are over 130 currently known different mutations that can cause the disorder, each with their own specifics, and also because<unk>  is an ion channel disorder, and ion channels are sensitive to internal and external environmental factors. It has been shown that pregnancy and the use of diuretics aggravate myotonia, and both these conditions are linked to the loss of divalent cations such as magnesium and calcium. It has further been shown that in pharmacological induced myotonia in isolated rat muscle, myotonia could be dampened by increasing the magnesium and calcium content of the extracellular medium. This has also been shown for isolated human muscle. Adrenaline/epinephrine is well known to make myotonia worse in most individuals with the disorder, and a person with<unk>  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<unk>  often appear very fit and able bodied, the general lack of knowledge about the disorder by the general and medical community, and often by the individual themselves, and the potential for inconsistency with the symptoms, many people with<unk>  have experienced a degree of social persecution at one time or another because of the effects of their disorder. Temperature Many patients report that temperature may affect the severity of symptoms, especially cold as being an aggravating factor. However, there is some scientific debate on this subject, and some even report that cold may alleviate symptoms. The warm-up phenomenon This phenomenon was described along with the disease by Thomsen in 1876 but its etiology remains unclear. Patients report that<unk>  may present itself in the following ways (this is from first hand experience). If the person is sedentary and then decides to walk up a set of stairs, by the third or fourth step their leg muscles begin to stiffen significantly, requiring them to slow down almost to a complete stop. But as the muscles loosen up, a few steps later, they can once again begin to climb the steps at a normal pace. If this person plays any kind of a sport, a good warm-up is mandatory. Otherwise if they need to quickly and intensively use their muscles, such as in a sprint race or a basketball game, their muscles will freeze up, causing them to slow down or almost come to a complete stop. But once the muscles are warmed up, they can once again function normally. This can happen in various muscles, even in muscles such as the tongue. For example, if a person has not spoken for awhile and then wants to speak, their tongue may be stiff at first causing the words to come out a little garbled, but after a few seconds of trying to speak, the tongue muscle will loosen up and then they can speak normally for the remainder of the time that they are conversing. Patients report that repeated contraction of muscle alleviates present myotonia with each contraction, such that myotonia is almost absent after a few contractions of the same muscle. The effect lasts about five minutes. There have been several proposed mechanisms for this phenomenon, but none have been conclusive; one theory is that the Na+/K+-ATPase is stimulated during the myotonic activity by increased intracellular Na+ in the cytosol of the muscle cell, increasing the activity of the Na+/K+-ATPase. However, in experiments with patients where the Na+/K+-ATPase had been blocked in the underarm by infusion of the Na+/K+-ATPase-blocker Ouabain, no effect on warm-up was observed. Another theory is that the few remaining functional chloride channels in muscle may become more active with increased muscle activity. It has been proposed that inactivation of Na+ channel 1.4 that resides in skeletal muscle, could play an important role in the warm-up phenomenon. In particular slow-inactivation of the channel is believed to have a spatial and temporal extend that is correlated to warm-up and therefore may provide a plausible cause.
Myotonia congenita
Myotonic dystrophy
Paramyotonia congenita
Periodic paralysis
Klumpke paralysis
Quadrigia
Cardiofaciocutaneous syndrome
Hyperkalemic periodic paralysis