Paramyotonia congenita (PMC) is a condition that affects the muscles. It usually begins in infancy or early childhood. The condition is also called Eulenburg disease or periodic paralysis. It can cause temporary episodes of being paralyzed. Symptoms include muscle weakness, stiffness, and fatigue.

Keep reading to learn the symptoms of PMC, what causes it, how it’s treated, and any complications that can result.

PMC is caused by a genetic mutation in the genes that control how muscles work in the body. People with this disorder are born with the condition. The primary symptoms are stiffness and weakness in the muscles, especially in the face, neck, arms, and hands. Episodes of muscle stiffness can last anywhere from a few minutes to several hours. Some people experience pain with the muscle stiffness, but others don’t. During episodes, movements may feel sluggish, or it may be difficult to do simple things like letting go of a glass.

PMC can also cause complete temporary paralysis. If you overexert your muscles, such as through exercise, they can quickly become very fatigued and completely paralyzed. Cold air can exacerbate the condition, but the weakness and stiffness can occur even in warm conditions.

PMC usually starts during infancy. A baby with PMC displays signs of clenched muscles that they can’t relax. Muscle weakness, on the other hand, usually begins during adolescence. PMC isn’t progressive, meaning it doesn’t get worse as you get older. Usually, people with PMC don’t have any muscle deterioration.

PMC is caused by a defect in the way that the muscle fibers in your body are activated. Normally, in order for a muscle to be activated, the body uses a sodium channel to activate a muscle. This is called muscle excitement. With PMC, a genetic mutation causes the sodium channel to remain open longer than necessary. That causes the muscle to become overexcited and unable to relax, which can lead to muscle stiffness. If the muscle contraction is prolonged, it may lead to weakness or even temporary paralysis.

PMC can be caused by a defective gene in one parent. If you have the condition, it most likely means that one of your parents also has the condition. However, PMC can sometimes happen randomly too, just like any other type of birth defect.

Will my child have PMC?

If you have PMC, it doesn’t necessarily mean that your child will have the condition. There is a 50 percent chance you could pass it on, because it only requires a defective gene from one parent, not both. If the gene is passed on, the severity of the condition can vary. Talk to a genetic specialist if you’re concerned about passing this condition on to a child.

PMC is an “invisible” illness, meaning you won’t look sick. In fact, you may even look athletic because of your overexcited muscles. PMC is diagnosed throughan electromyographic (EMG) examination. This test uses needles to record the electrical signals that your muscles send out during activation and use. The test cools the muscle down to bring on the condition.

It can be difficult to reach a diagnosis of PMC. You may need to work with your doctor to rule out other conditions before being diagnosed with PMC.

There’s no cure for PMC. Treatment of the condition is usually managed by many different health experts, including a physical therapist and a primary care provider. You also need to look for any triggers and learn the signs that an episode of paralysis is about to happen.

Some medications may help manage symptoms of PMC, such as:

  • mexilentine (Mexitil), which is a sodium-channel blocker
  • paroxetine (Paxil, Pexeva), which is a selective serotonin reuptake inhibitor

You may also need special accommodations, such as a handicapped parking permit so you don’t have to walk long distances.

Most people with PMC can live a relatively normal life. The most important thing you’ll need to do is avoid getting very cold or overexerting your muscles. Weather changes can also trigger PMC. If you have hyperkalemic periodic paralysis as well, you may need to avoid certain potassium-rich foods, such as cantaloupes, peaches, bananas, and prunes.

PMC is not life-threatening, and the outlook for living with the condition is good. Work with your doctor to come up with a treatment plan to manage your symptoms.

Invisible illnesses like PMC don’t always get the funding and attention that they need because they’re less visible. That’s why it’s important to raise awareness. Today, more research is being done into inherited myopathy diseases such as PMC. You can get involved in raising awareness and funds, or get support for PMC at the MDA website.