Hypokalemic periodic paralysis (hypoPP or hypoKPP) is a rare disorder in which a person experiences episodes of painless muscle weakness and often paralysis. It’s the most common of several genetic disorders that cause periodic paralysis.
There are two types of hypoPP:
- Paralytic: This form is most common. In the paralytic form, intermittent, temporary episodes of muscle weakness or paralysis are experienced.
- Myopathy: This form is characterized by permanent muscle weakness, fatigue, and pain. More than 74 percent of older people with hypoPP experience myopathy. One of the first symptoms of myopathy is weakness or paralysis of the legs, brought on by exercise.
People usually experience their first attack between the ages of 10 and 14. Attacks occur randomly, but are often triggered by factors like foods or exercise. It’s very common to experience an attack after waking from sleep.
The attacks vary in severity from mild muscle weakness to significant paralysis. They can last anywhere from several hours to several days. The frequency of attacks also varies from person to person. Some people experience them daily, whereas others experience them a few times a year.
As a person ages, they may experience fewer episodes of paralysis. Instead, they have what are called abortive attacks. This refers to general muscle weakness lasting longer periods of time.
Common symptoms include:
- heart palpitations
- weak or cramping muscles, most often in the arms, legs, shoulders, and hips
HypoPP attacks are caused by not having enough potassium in your body. As potassium ions dissolve in your body, they pick up a positive electric charge. This charge enables them to conduct electricity and send signals throughout your body. Potassium ions perform many tasks in your body, such as transmitting nerve impulses.
One on the most important functions of potassium is to help your muscles contract. Your muscles work by alternating between contracting and relaxing. This is what operates all the muscles in your body.
Ions are pumped in and out of cells by ion pumps in the cell membranes. They travel in your body through tunnel-like protein channels.
People who have hypoPP have mutations in their genes that change the way these protein channels work. As a result, they don’t have enough of the potassium needed for their muscles to contract. This is what causes the muscle weakness and paralysis.
The condition is an autosomal disorder. This means that it can be passed down through families. If one parent has the gene that causes hypoPP, their children will develop hypoPP.
However, some people have hypoPP without any known family history of the disorder.
Although episodic triggers vary for each person, episodes of paralysis are often brought on by:
- sugary or starchy foods
- salty foods
- going too long between meals
- eating a very large meal
- high levels of physical exertion
- temperature extremes
- strong emotion
- certain medications, such as anesthesia
HypoPP is often hard to diagnose. There are no tests for the disorder, and symptoms aren’t evident unless you’re observed during an attack.
If you’re experiencing symptoms characteristic of hypoPP, consult your doctor. Your doctor will ask you to:
- Describe your symptoms.
- Explain what time of day you have symptoms.
- Describe what you were doing just before the event.
If you have a family history of hypoPP, be sure to tell your doctor. This can help them evaluate your symptoms and make a diagnosis.
If you experience an attack during your appointment, your doctor may:
- have your blood tested to determine potassium levels
- examine you to see if there is a decrease in your muscle reflexes
- order an electrocardiogram if you’re having an irregular heartbeat or related cardiac symptoms
Treatment consists of diet changes and avoiding things that trigger your attacks. Your doctor may also want to treat you with medications.
Treatment involves avoiding your known triggers. For example, if salty foods typically bring on an attack, limiting or removing these from your diet may help.
Talk with your doctor about your known triggers. They can help you devise a management plan.
Your doctor may also prescribe the following:
- Carbonic anhydrase inhibitors: These medications increase the flow of potassium. Common options include dichlorphenamide (Keveyis) and acetazolamide (Diamox).
- Potassium supplements: Oral potassium supplements may be given to help stop an attack that’s in progress. Your doctor will advise you on proper dosage.
See your doctor
Although rare, some people may experience more serious attacks that require immediate medical attention.
Symptoms that warrant a trip to the emergency room include:
- irregular heartbeat, called arrhythmia
- difficulty breathing
- trouble swallowing or speaking
- loss of consciousness
HypoPP is rarely life-threatening. Diet and lifestyle changes to avoid known triggers may help reduce your number of attacks. Some find the disorder is controlled well by a combination of these steps and prescribed medication. Talk to your doctor about your options. They can help devise the best treatment.
Although hypoPP can’t be prevented, you can take steps to reduce how often you experience an episode and help reduce the severity.