Hypokalemic Periodic Paralysis

Hypokalemic periodic paralysis (hypoPP) causes sudden episodes (attacks) of extreme muscle weakness or paralysis. These attacks can last for hours or even days. This rare genetic condition can start in childhood, teen years or adulthood. Most people have their first attack before age 35.

Hypokalemia means potassium levels in your blood are too low. Potassium is a mineral that helps your muscles work. During attacks, you may have low potassium in your blood.

When an attack happens, it can feel overwhelming. Your body may not move the way you expect, and that can bring fear or frustration. Getting a clear diagnosis can take time. But once you have it, you and your healthcare provider can work on a plan to manage symptoms.

Treatment may not stop every attack, but it can reduce how often they happen and how severe they feel.

Types of hypokalemic periodic paralysis

There are two main types. Each links to a different gene. These affect how your muscles work:

• Type 1: This is the most common type. A genetic change in the CACNA1S gene causes it. This change affects calcium channels, which play a role in muscle contractions. When these channels don’t work as they should, your muscles may not respond the right way.
• Type 2: A genetic change in the SCN4A gene causes this type. This change affects sodium channels. These channels control the electrical signals that tell your muscles when to move. Problems with these channels can make attacks start suddenly.

Hypokalemic periodic paralysis symptoms

The main symptom of hypoPP is sudden muscle weakness or paralysis. It usually affects your arm or leg muscles. It also usually affects your legs before your arms and neck.

You might notice that weakness:

• Can occur every day, weekly, monthly or only once in a while
• Lasts minutes up to 72 hours
• May happen with or without triggers
• Starts suddenly, often when you wake up or in the middle of the night

Before an attack, you might also notice:

• Mood changes
• Pins-and-needles feeling in your arms and legs
• Reduced or missing reflexes
• Tiredness

Between attacks, you usually get your muscle strength back. You may have mild weakness at times, but light exercise might improve it.

Triggers of hypokalemic periodic paralysis attacks

Certain things can set off attacks if you have hypoPP. These include:

• Rest after hard exercise
• Eating large meals with lots of carbs
• Eating too much salt
• Drinking alcohol
• Being in cold temperatures
• Feeling stress, fear or excitement
• Taking certain medicines like anesthetics or corticosteroids

Your healthcare provider may recommend avoiding these triggers to help lower your risk of attacks.

Hypokalemic periodic paralysis causes

A genetic change (mutation) causes hypokalemic periodic paralysis. These affect how sodium or calcium channels work. The channels control how your muscles move.

In hypoPP, sodium channels may stay open too long. When this happens, too much sodium flows into muscle cells. It disrupts the normal electrical signals. This keeps your muscles from firing signals the right way.

Calcium channel problems affect how your muscles tighten (flex) and move. When either channel doesn’t work as it should, your skeletal muscles can’t contract properly. This leads to sudden episodes of muscle weakness or paralysis.

Researchers have found several gene variants that cause most hypoPP cases, including:

• CACNA1S
• SCN4A
• KCNJ2

You inherit these gene changes in an autosomal dominant pattern. This means if just one of your biological parents has the variant, you can develop the condition.

Risk factors

Your risk is higher if someone in your biological family has hypoPP. Most cases happen because of a genetic mutation, so there’s no way to prevent them.

If you or your partner has hypoPP and plan to have biological children, you may want to meet with a genetic counselor. A counselor can explain your risk of passing the condition on and answer your questions.

Complications of hypokalemic periodic paralysis

Rarely, this condition can affect the muscles you use to breathe. But this can be life-threatening and requires immediate medical attention.

In some cases, low potassium during an attack can also cause irregular heart rhythms.

You might develop persistent muscle weakness later in life. It’s more common in your legs and hips because of muscle damage. Some people only have mild weakness. But others may develop severe weakness that limits daily activities or requires a wheelchair.

How doctors diagnose hypokalemic periodic paralysis

A healthcare provider will start by asking about your symptoms and your biological family health history. They’ll offer tests to learn more about the symptoms you have. Testing helps rule out conditions that cause similar symptoms. These could include:

• Potassium blood test: Your provider may use this test to check for low potassium levels during episodes of paralysis.
• Genetic test: This test can identify the genetic variants that cause hypoPP.
• Electromyography (EMG): This test checks how your muscles and the nerves that control them are working. It can be done during or between attacks.
• Thyroid function test: This test measures thyroid hormone levels (TSH, T3 and T4) to rule out hyperthyroidism
• Electrocardiogram (ECG): This test looks at your heart’s electrical activity and can show changes linked to low potassium.

Some providers may also use an exercise test during an EMG to look for muscle changes between attacks.

Hypokalemic periodic paralysis treatment

There’s no cure for hypokalemic periodic paralysis. But treatments can help you manage the condition and lower your risk of complications.

To treat paralysis attacks right away, your healthcare provider may recommend:

• Oral potassium chloride: This may improve muscle weakness during an attack. You may need more than one dose.
• Low-level exercise: This is for mild attacks. Gentle movement can sometimes reduce symptoms.
• IV potassium in a hospital: This is only if you have irregular heart rhythms, swallowing problems or breathing muscle paralysis.

Your provider may also recommend options to prevent future attacks:

• Lifestyle changes: You should avoid known triggers when possible. A dietitian may help you plan meals with more potassium-rich foods and fewer high-carb or high-salt foods.
• Medications: Long-term medicines can help keep potassium levels stable and reduce attack frequency.
• Physical therapy: This helps you maintain your muscle strength and function.

Hypokalemic periodic paralysis medications

Medications vary based on your body’s needs. Your treatment plan may include:

• Potassium supplements: These help maintain stable potassium levels.
• Carbonic anhydrase inhibitors (acetazolamide): These may reduce attack frequency and improve muscle strength. They tend to work better if you have a CACNA1S gene variant.
• Dichlorphenamide: This is U.S. Food and Drug Administration (FDA)-approved as a first-line option or for people who don’t respond well to acetazolamide. It can reduce how often attacks happen and how severe they are.
• Potassium-sparing diuretics (spironolactone, triamterene): You can use this alone or with other medicines to regulate potassium levels.

When should I see my healthcare provider?

If you have hypokalemic periodic paralysis, you’ll need regular visits with your healthcare provider. They’ll check your symptoms and potassium levels to make sure your treatment plan is working.

Call your provider right away if:

• Attacks become more frequent or severe.
• You have trouble breathing or swallowing during an attack.
• You notice new or ongoing weakness between attacks.
• You have irregular heartbeats, chest pain or feel faint.

Managing hypoPP can sometimes feel stressful. If the condition affects your mood or daily life, consider talking with a mental health professional. They can help you cope with the challenges of living with this condition.

What’s the prognosis for hypokalemic periodic paralysis?

The outlook is different for each person. Some people have only a few mild attacks, while others may have more frequent or severe ones. Attacks may be less frequent as you get older (after the age of 30), but some people might start developing permanent weakness.

Most people can manage the condition with medications and by avoiding triggers. Still, severe attacks can sometimes be serious and may require hospital care. Living with frequent episodes can also affect your work, social life and emotional well-being. Treatment options are available to help you manage the physical and emotional effects of this condition.

Life-threatening complications aren’t common. In rare cases, serious problems, like breathing trouble or pneumonia, can lead to early death. Your healthcare provider can work with you to lower these risks and help you manage symptoms safely.