Blood potassium levels can sometimes rise during attacks, too. “Hyper” means that there is a high amount of something, and “kalemic” refers to potassium in blood. There is another periodic paralysis type with a similar name, “hypokalemic,” so it’s important to not confuse the two types.

Symptoms 

Hyperkalemic periodic paralysis causes sufferers to have attacks of extreme muscle weakness, stiffness, or paralysis. These attacks usually last from around ten minutes to an hour, but in some cases, they can stretch on for one or two days. Frequency of attacks can vary greatly between different people. Some people have attacks every day, others have them several times per month, while there are others who have them every few months or less often. The strength of the attacks isn’t always consistent — sometimes, the patient feels fatigued, but can still move around slowly. Other times, they aren’t able to move at all. The onset of muscle weakness is gradual and does not cause “drop attacks”.  On the other hand, an affected individual may underestimate the severity of a developing episode while seated and then suddenly fall when attempting to walk. 

These kinds of attacks can affect one area of the body or multiple areas. Even the facial muscles can be affected, meaning that patients might find it difficult to make facial expressions due to stiff muscles.. Regional muscle stiffness may improve over a few minutes with repeated efforts for the same muscle group (warm up). Muscle stiffness is known as myotonia. If the loss of force has not progressed to full paralysis, then light exercise may enhance the return of strength.

Attacks of hyperkalemic periodic paralysis can be triggered when the potassium level increases in their blood (AKA serum potassium). Potassium levels may rise during attacks, but not always. Then, as the attack is ending, the blood potassium returns to the normal range or may even  drop to a lower than normal level for a short time. This temporary potassium drop should not be mistakenly diagnosed as hypokalemic periodic paralysis. The patient is really hyperkalemic. These shifts of blood potassium levels over time is why establishing a diagnosis of hyperkalemic or hypokalemic periodic paralysis is not as simple as a blood test for potassium.

Individuals with HyperPP have varying degrees of transient muscle stiffness (myotonia) and episodes of weakness. If the predominant feature is muscle stiffness that is aggravated by cold temperatures and paradoxically worsens over the first few repeated attempts of movement, then this disorder is usually called paramyotonia congenita (PMC).  HyperPP and PMC have overlapping conditions with similar symptoms, similar biological mechanisms, and similar treatment plans.  Within one family, some affected members may be more “HyperPP-like” while others are more “PMC-like”, even though they all share the same channel mutation.

Many patients with HyperPP will eventually develop a slowly progressive permanent muscle weakness, which is called myopathy. This might happen as the patient reaches their 50s or 60s. Some patients with myopathy use a wheelchair or scooter to help them get around outside the house to ease the strain on their weakened muscles. However, they are still able to have fulfilling lives and do many kinds of activities.

Triggers

People who have hyperkalemic periodic paralysis must try to avoid situations that trigger their attacks. Because this type of periodic paralysis is hyperkalemic, one major attack trigger is eating potassium-rich foods. Blood potassium often increases while fasting, which may trigger an attack. Another example of a common trigger is being in a cold environment, so going outside in cold weather can cause an attack to happen. Stress can be a trigger as well. The more stress a patient feels in their day-to-day life, the more likely it is that they will have an attack.

Another common trigger is resting after exercise. However, even without exercising, it’s possible to have an attack just from not moving for a long period of time, such as when sitting through a movie. Sleep is also a trigger because of the fact that sleeping involves being inactive for a long period of time. Patients often have attacks in the morning when they wake up, making it hard to get out of bed.

Because there are many triggers and different people will have different triggers, it is recommended that patients keep a trigger diary. After you have an attack, you should write down what happened, how you felt, what you were doing before the attack, and how you were able to recover from it. After doing this for a while, you’ll be able to look back on your previous diary entries and notice certain patterns.

Diagnosis

Hyperkalemic periodic paralysis symptoms almost always begin during the childhood or teen years. The frequency of attacks can change throughout the patient’s lifetime. Usually, the attacks start out not being very frequent, but as the patient reaches their 30s, there are more attacks. Then, in their 50s, the patient might have fewer attacks, but their muscles have been permanently weakened (myopathy).

The impact that this disorder can have on a person’s life is determined by how many years went by before they received a correct diagnosis. Because it is such a rare disorder, doctors often mistake it for other more common conditions. This results in patients spending a large portion of their lives with the wrong diagnosis, which means they are not receiving the proper treatment. Getting the right diagnosis makes a big difference!

Giving doctors your family’s health history and your trigger diary can help them come closer to a periodic paralysis diagnosis, and there are other diagnostic tools available, too. Hyperkalemic periodic paralysis is a genetic disorder, and commercial lab genetic tests can be performed that can detect the disorder in some patients. However, genetic testing is not perfect and does not always detect all cases. Another diagnosis method is the Compound Muscle Action Potential test, which measures the electrical activity of muscles. This test can’t always detect periodic paralysis, but it can do so in a lot of cases.

Treatment

Attacks of hyperkalemic periodic paralysis can vary in severity. For more mild attacks, it’s possible to do simple things to recover, such as eating or drinking a high-carb food or beverage or slowly making small movements in order to work off muscle weakness or stiffness. Medication might be needed if these methods don’t work. Albuterol inhalers may hasten recovery from weakness and potassium-wasting diuretics may reduce attack frequency or severity. Medications that inhibit carbonic anhydrase (acetazolamide or dichlorphenamide) may be taken regularly to reduce the likelihood of having an attack. Dichlorphenamide (KEVEYIS)  is the only FDA-approved drug for symptom management in periodic paralysis. Severe attacks might affect the heart or breathing, so patients experiencing a severe attack must receive hospital treatment. 

Patients should try their best to live a lifestyle that prioritizes minimizing triggers when possible. Living somewhere with a warm climate can help reduce the chances of an attack happening. Keeping stress levels low is another important way to make attacks less likely to happen. Avoid exercise that is overly intense, because resting after an intense workout can be a trigger. Planning your diet carefully is necessary to have fewer attacks because it’s crucial to stay away from potassium-rich foods.

Your Next Steps

If you think you may have hyperkalemic periodic paralysis, please talk with your doctor. Speaking with a doctor about a rare disorder can be intimidating, and many doctors have little to no prior knowledge about periodic paralysis. The PPA has many resources to help you become a better advocate for yourself. Click here to learn about other types of periodic paralysis. You can also submit a question to our Ask the Experts panel. Remember, we are here to support you all the way as you take action to advocate for your health!