Hyperkalemic Periodic Paralysis

Hyperkalemic periodic paralysis (hyperKPP or HYPP) causes sudden episodes (attacks) of muscle weakness or temporary paralysis. It happens when potassium levels in your blood get too high.

Hyperkalemia means your blood has more potassium than normal. Potassium is an important mineral that helps muscles contract and work properly. During an attack, the extra potassium can get in the way of muscle control.

Attacks for this rare genetic disorder often last 15 minutes to an hour. But sometimes, they may be longer. The condition can start in childhood, adolescence or early adulthood. Many people notice their first episode before age 20.

Treatment may not stop every episode, but it can make attacks happen less often.

Hyperkalemic periodic paralysis symptoms

HyperKPP mostly affects the muscles in your arms and legs. The symptoms come and go, which means they shouldn’t last forever. Common symptoms include:

• Muscle weakness or paralysis
• Muscle stiffness
• Problems relaxing

After an attack, muscle control usually returns. You might have mild stiffness in your face and hands between attacks.

Hyperkalemic periodic paralysis triggers

Certain things may cause hyperKPP symptoms. These may include:

• Eating potassium-rich foods, like bananas, leafy greens and potatoes
• Drastic temperature changes (hot or cold)
• Rest after physical activity
• Taking potassium supplements
• Stress

Triggers are different for each person and aren’t limited to this list. A healthcare provider will give you advice to avoid triggers. Avoiding triggers could prevent future attacks.

Hyperkalemic periodic paralysis causes

A change (mutation) of the SCN4A gene causes hyperKPP. This gene gives your body instructions to make a protein that regulates sodium channels in your muscles. Sodium channels help move sodium in and out of muscle cells. Your muscles need this to tighten and relax.

In hyperKPP, the SCN4A channels don’t work the right way. Sometimes, they stay open too long or don’t close when they should. This allows too much sodium to go into your muscle. The extra sodium causes potassium to leak out of your muscle cells. These changes affect how your muscles contract. This can lead to sudden episodes of weakness or paralysis.

Risk factors

You’re more likely to develop this condition if you have a biological parent with it. HyperKPP passes down in families through an autosomal dominant inheritance pattern. This means you only need to get the genetic change from one parent to develop it.

A genetic counselor can help you understand your risk of passing this condition on to your future children through genetic counseling.

Some cases may happen randomly. This means you don’t have any history of the condition in your family.

Complications of hyperkalemic periodic paralysis

HyperKPP can lead to other health problems over time. Some may be mild, while others can be more serious. Possible complications include:

• Attacks that get worse or happen more often as you age, especially after 50
• Episodes that affect the muscles used for breathing (this can be fatal)
• Long-term muscle pain and fatigue
• Worsening and ongoing muscle weakness

A smaller number of people may develop a more serious problem called myopathy. This is damage that happens to your muscles over time.

It’s important to talk to your anesthesiologist about this condition prior to any surgery because some anesthetics can lead to complications, like complete paralysis, breathing issues and body temperature fluctuations.

How doctors diagnose hyperkalemic periodic paralysis

Your healthcare provider will ask about the symptoms you have and about your biological family health history. They’ll want to know when the episodes started, how long they last and what triggers them.

Tests may help diagnose it. They can also rule out conditions with similar symptoms. Tests may include:

• Electromyography (EMG): This test checks how well your muscles and the nerves that control them are working.
• Genetic test: This test looks for a genetic variant in the SCN4A gene.
• Long exercise test: In this test, you’ll repeatedly use a muscle. A provider records how the muscle responds.
• Potassium blood test: This test checks potassium levels in your blood.

Hyperkalemic periodic paralysis treatment

Treatments may help manage symptoms and reduce how often attacks happen, but there isn’t a cure.

To treat attacks when they start, your provider may suggest:

• Mild exercise at the beginning of an episode
• Eating a carbohydrate snack to lower potassium levels
• Using a beta-agonist inhaler (like salbutamol) to quickly lower potassium

In rare or severe cases that affect the muscles that help you breathe, you may need treatment in a medical setting with an IV of calcium gluconate.

For long-term management, your healthcare provider may recommend:

• Avoiding triggers that can cause attacks
• Meeting with a dietitian to help you create a customized meal plan
• Taking medications to reduce how often attacks happen (like dichlorphenamide) or to lower potassium levels (hydrochlorothiazide)

When should I see my healthcare provider?

If you have hyperKPP, you’ll need regular check-ups. These visits help your provider see how symptoms are changing and if your treatment plan is working.

At these visits, the provider may:

• Run blood tests to check potassium levels.
• Review your symptom history and look for new triggers.
• Adjust medicines or meal plan recommendations if needed.
• Order an MRI of your muscles every few years if muscle weakness gets worse.

Call your provider sooner if:

• Attacks become more frequent or severe.
• Weakness doesn’t go away after an attack.
• You have breathing problems, trouble swallowing or chest weakness during an episode.

What can I expect if I have hyperkalemic periodic paralysis?

It’s hard for healthcare providers to know exactly how hyperKPP will affect you over time. The condition doesn’t look the same for everyone. Episodes may become more common as you age. But some people have fewer episodes as they grow older. Your provider can give you a specific prognosis. That way, you’ll know better what to expect.

But living with uncertainty can be stressful. If hyperKPP starts to affect your emotional health, reach out to a mental health provider.