Frequently Asked Questions About Hyperkalemic Periodic Paralysis
What is HyperKPP and what are its symptoms?
Hyperkalemic Periodic Paralysis is a rare inherited disorder which causes episodes of paralysis or weakness. It was only identified as a separate disorder in 1955.
Hyperkalemic periodic paralysis causes attacks of muscle weakness and (in some patients) muscle stiffness. The attacks of weakness are usually brief (many attacks may only last a few minutes) but they may include muscle pain and an irregular heartbeat. Patients may experience brief episodes of localized weakness in a hand, foot, jaw or limbs or they may experience generalized paralysis. These episodes often occur during rest after exercise, and they may occur on awakening in the morning. Attacks may develop quite rapidly, causing unexpected falls.
The muscle stiffness (medical term 'myotonia') may come and go or it may be more or less constant. In myotonia the muscle fibers are slow to relax after contraction. Some patients are very athletic in appearance due to the myotonia, but appearances can be deceiving as these well-developed muscles are often quite weak. For some patients myotonia is painless, for others it is painful.
What causes HyperKPP?
The periodic paralyses are caused by abnormalities in the ion channels (especially the sodium, calcium and potassium channels) of the muscle membrane. The ion channels control the movement of sodium, chloride, potassium and calcium across the cell membrane and from one cell compartment to another. This movement of ions produces the electrical 'spark' which allows our muscles to move.
Hyperkalemic periodic paralysis is caused by a flaw in a sodium channel in the muscle membrane. This flaw makes the person with HyperKPP extremely sensitive to increases in serum potassium that wouldn't bother the average person. Anyone can be made weak by a drastic increase in serum potassium, but the person with HyperKPP gets weak with even a slight elevation in potassium level, and patients with HyperKPP may become profoundly paralyzed while their potassium levels remain well within normal limits, even when their potassium is on the lower end of normal.
Weakness most commonly affects the muscles of the arms and legs but may affect the trunk as well. In a few patients the muscles involved in breathing can be affected during severe episodes.
An irregular heartbeat can occur during episodes as well. Most patients have normal muscle strength between attacks, but muscle tissue can be damaged by attacks and this damage may eventually cause permanent weakness in some patients once they reach their 50s and 60s.
During episodes of muscle weakness the normal flow of sodium ions is interrupted affecting the ability of the cell to contract properly. The potassium level in the blood may not rise during attacks, but many HyperKPP patients have a slightly elevated potassium level between attacks.
My potassium level is never outside of the normal level yet the doctor says I have Hyperkalemic periodic paralysis. Why does she call it that?
The term 'hyperkalemic' is somewhat confusing, because in most patients the level of potassium in the blood does not rise above normal during attacks. 'Hyperkalemic' refers to the fact that attacks may be triggered by eating potassium-rich foods or by giving the patient potassium. So-called 'normokalemia' has now been genetically identified as one of the sodium-channel disorders. The general opinion is that Normokalemic PP is a variant of Hyperkalemic PP.
No one in my family has this disease. How did I get it?
In a majority of cases HyperKPP is inherited, but a person may carry, and pass on, the defective gene without ever experiencing any symptoms at all. But some cases just happen, like any other birth defect, for reasons which are unclear.
Will I pass this on to my children? How does inheritance work?
The chances that a child of an affected person will inherit the defective gene is 'statistically' 50%, but not all who inherit the gene will have symptoms. The degree to which children are affected may vary from one child to the next. One child may be mildly affected, the next seriously affected and the next unaffected. Even identical twins may be affected to different degrees.
What triggers attacks?
Some episodes of HyperKPP are triggered by food. Food triggers are generally those which are high in potassium. Fruits high in potassium include cantelopes, apricots (fresh and dried) dried figs, kiwi fruit, peaches, raisins, banana and prunes. Fruit juices are high in potassium, especially orange and pineapple juice and apricot and peach nectars. High potassium vegetables include artichoke, parsnip, potato, pumpkin, spinach, broccoli, brussels sprouts, cauliflower, tomato juice"347;puree and V-8 juice. Lentils and beans are high in potassium. Other foods that are high in potassium include nuts, peanut butter and chocolate.
Other common triggers include both rest after activity and periods of inactivity (for example; sitting through a long class or church service, especially in a cool room). Sleep is a potent trigger. Going too long without eating is another trigger. HyperKPP patients can't let themselves get too hungry. Getting chilled is a trigger. Eating or drinking cold foods or beverages may provoke attacks in sensitive individuals. Weather changes seem to affect HyperKPP patients adversely. Hydrocarbons like gasoline fumes, paint fumes or car exhaust have been reported as triggers by some patients. Alcohol is another trigger for most HyperKPP patients, especially alcoholic drinks rich in ethanol.
HyperKPP episodes are often brief (minutes to an hour) and may be infrequent, though some patients have many per day. Patients learn that they have to stay warm, avoid unaccustomed heavy exercise, and not sit still too long at a time. Many find they can abort a developing episode by drinking a sweet beverage (a soda or heavily sweetened tea) or eating a high carbohydrate food like candy when they feel an episode developing.
How can I determine what causes my attacks?
See How to Determine Episode Triggers.
How do I avoid having attacks?
Learn to determine your triggers and avoid them. For some people this is enough. For others medication is necessary.
What medications are prescribed for HyperKPP?
A tablespoonful of Calcium Gluconate syrup stirred into a glass of Coca Cola or other sweet beverage has proven an effective therapy which aborts mild episodes in the early stages. Calcium Gluconate Syrup is a mineral supplement available off the shelf and is found in most pharmacies. Albuterol, administered by nebulizer or inhaler, has proven an effective treatment for some patients who have infrequent episodes. For those who have frequent episodes and whose lives are compromised, more aggressive treatment is advisable, especially since some patients with HyperKPP may develop permanent muscle weakness after years of episodes.
The carbonic anhydrase inhibitor 'Diamox' (acetazolomide) is often prescribed for HyperKPP patients. About 25% of patients do not respond to Diamox and must be put on other drugs.
Patients who take Diamox must be alert to potentially dangerous drug interactions as it slows the excretion of other drugs from the system. Avoid large doses of aspirin when taking Diamox. Some other commonly used drugs to be cautious with when taking Diamox include barbiturate medicines used for inducing sleep or treating seizures, the ephedrines (found in some over the counter asthma inhalers), antidepressants, the heart drug Mexitil (mexiletine) which is often prescribed for the myotonia found in HyperKPP, steroids and diuretic medications ('water pills'). This is not an exhaustive list. Always discuss all other medications you are taking with your physician when starting a new drug.
Other medications used to treat HyperKPP include the potassium-wasting diuretics - Lasix (furosemide), Hydrodiuril (hydrochlorothiazide), etc. For those who have significant myotonia, the anti-arrhythmic drug Mexitil (mexiletine) is used in low doses; 50-150 mg daily is reported to be adequate by patients. Very low doses of Paxil (paroxetine) (10-20 mg daily) have also been reported to help relieve myotonia.
What tests are used to diagnose HyperKPP?
A variety of tests are used. Since most episodes are brief it may be difficult to 'catch' a patient during a spontaneous episode. But several blood tests taken over a period of a week or two to measure the level of potassium in the blood may suggest the diagnosis, since potassium levels are frequently higher during attack-free intervals.
Patients with HyperKPP often have an accompanying muscle condition called myotonia, which may be found during Electromyographic examination. Evidence of myotonia supports the diagnosis of HyperKPP. At times diagnosis is not as easily accomplished, and further testing is necessary. There is more information about diagnosis in other articles on this website. See The Exercise EMG.
Where is the best place for treatment of periodic paralysis?
The best place for treatment is almost always the patient's own family physician, if that physician is willing to read about the condition and learn how to manage it. Every patient responds a bit differently to treatment and the members of our group who are, on the whole, the most satisfied with their care are those who are cared for by the person who cares for their overall health. Common illnesses like a 24-hour stomach flu can turn into life-threatening emergencies for a HyperKPP patient, and in these instances there is no time or opportunity to go to a far away specialist.
Who is doing research on HyperKPP?
There are a number of research teams working on the Pps. Research is concentrating on the genetics and mechanics of the channelopathies, rather than on therapy and management. There's been nothing new in the way of therapy for many years, although we have learned how to apply therapies much more effectively, and we've made great strides in management.
Can I have a DNA test for HyperKPP?
Genetic testing is available, but it is not yet reliable enough to diagnose all HyperKPP patients. While a genetic test may be able to say you have HyperKPP, if the results of the test is negative that does NOT mean you do not have the disorder, as researchers know there are a number of variants which they have yet to be able to identify. If you plan to be tested it is wise to talk about this issue with your physician ahead of time, just in case your test comes back negative (as most are still doing at this point). Make certain you will not be denied therapy by your physician or HMO should the test be negative!
Will I be able to lead a normal life?
Most people with HyperKPP lead reasonably normal lives. Many cases of HyperKPP are mild, and even those who are severely affected can have their symptoms eased through medication and attention to diet and lifestyle issues. There is no cure, but most patients manage to lead well-rounded and fulfilling lives. There is no denying that some patients have physically-compromised lives, especially patients with a long history of frequent and severe episodes. But many are quite active. Members of our Listserv group come from all professions and walks of life including physicians, nurses, teachers, lawyers, musicians, engineers, journalists, farmers and ranchers, a plantation owner, homemakers, accountants, and computer specialists.
Will my life be cut short by HyperKPP?
Several of our families have affected members who have lived well into their 80's, in complete control of their mental faculties and capable of independent life until the end of their lives.
Will I end up in a wheelchair?
This is a hard question to answer. Permanent muscle weakness is a fact of life for many older patients, and activities like climbing stairs and walking long distances may become very fatiguing. Any number of our older members use a wheelchair or 'scooter' outside the home, but are mobile and on their feet inside the house. Very few rely on a wheelchair full time unless their condition is complicated by other problems.
We hope we have answered some of your basic questions about Hyperkalemic Periodic Paralysis. For medical references see our Physician's Sheet: Hyperkalemic Periodic Paralysis.