Hypokalemic Periodic Paralysis FAQ
What is Hypokalemic Periodic Paralysis (HypoKPP) and what are the symptoms?
Hypokalemic Periodic Paralysis is a rare inherited muscle disorder that causes episodes of paralysis or weakness. During severe attacks the patient may become totally unable to move and even appear unconscious. Despite being unable to speak or open their eyes the patient is awake and completely aware of their surroundings during attacks.
Patients with HypoKPP typically begin showing symptoms in the first or second decade of life, often as they enter puberty. About 65% develop symptoms before the age of 16, but first symptoms have been documented in patients as old as 60-70 years. In patients who develop symptoms at a young age attacks may be infrequent at first, but eventually may occur daily.
Episodes may last anywhere from an hour or two to days, and may vary in intensity from episode to episode, with mild localized weakness in a hand, foot, jaw or limbs one time and generalized paralysis the next. Episodes may be accompanied by extreme muscle tenderness and aching or be entirely painless. Patients may also have what are called abortive attacks - fluctuating daily weakness which lasts for extended periods and has even been mistaken for permanent weakness by physicians. This type of weakness becomes more common in patients as they enter their 40s and in some patients abortive episodes may replace paralytic episodes. Patients often find abortive attacks are more disabling than brief episodes of paralysis.
Weakness most commonly affects the muscles of the arms and legs but may affect the trunk as well. Weakness occasionally affects the eyelid muscles (causing droopy lids). In a few patients the muscles involved in breathing and swallowing can be affected during severe episodes. An irregular or weakened heartbeat can occur during episodes as well. Most patients have normal muscle strength between attacks, but muscle tissue is damaged by attacks and this damage may eventually cause permanent weakness in some patients once they reach their 50s and 60s.
What happens to make me weak during episodes?
During episodes of muscle weakness, potassium flows from the bloodstream into muscle cells, affecting the ability of the cell to contract properly. Potassium levels usually fall during attacks but are normal between attacks.
What causes HypoKPP?
All of the periodic paralyses are caused by abnormalities in the ion channels (especially the sodium and calcium 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. Hypokalemic Periodic Paralysis is caused by a flaw in an ion channel in the muscle membrane. This flaw makes the person with HypoKPP extremely sensitive to decreases in serum potassium that wouldn't bother the average person. Anyone can be made weak by a drastic lowering of serum potassium, but the person with HypoKPP gets weak with even a slight fall in potassium level, and patients with HypoKPP may become profoundly paralyzed while their potassium levels remain within normal limits.
No one in my family has this disease. How did I get it?
In a majority of cases HypoKPP 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 and 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 who 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.
“My potassium level is never outside of the normal level yet the doctor says I have Hypokalemic Periodic Paralysis. Why does she call it that? Wouldn't it be better to call it Normokalemic Periodic Paralysis?”
Those with HypoKPP have episodes during which the potassium usually falls. It may only fall by a fraction of a point, and it may never fall below normal, but it usually falls a little. If it does not other criteria may be applied. Those with HypoKPP often respond with an attack of weakness to the administration of carbohydrates (such as a drink of glucose). This weakness disappears when the patient is given potassium, either to drink or by IV. Other simple tests can be applied. In HypoKPP the urine the patient produces during an attack of serious weakness or paralysis can be collected and analyzed. Patients with HypoKPP stop excreting potassium during attacks. This is probably because so much of the potassium in the blood moves into the muscle cell during episodes. Patients with NormoKPP usually react with an attack of weakness to potassium administration. Genetically some cases of so-called ‘NormoKPP’ have now been proven to be a variant of HyperKPP.
What triggers attacks?
Many episodes of weakness are triggered by food. Food triggers include sweet or sugary foods or starchy foods. These are foods like candy, cakes, desserts, soft drinks which are sweetened with sugar, fruit juices, bread, cereal products, rice, potatoes, and pasta. Foods like these are processed by the body very quickly and raise the blood sugar rapidly. The pancreas responds to this rapid rise in blood sugar by producing a lot of insulin. Insulin drives potassium from the blood into the cell, which triggers weakness. Salty foods, like burgers or potato chips, are a trigger for many HypoKPP patients. Getting too hungry, or eating a large meal (especially if you are very hungry) triggers episodes in many patients.
Other common triggers include unusual activity or exercise - usually the day before the attack, but sitting still for too long may also trigger episodes. Patients learn that pacing their activities is absolutely vital to gaining control. Sleep is a potent trigger, and many patients wake up paralyzed. Getting too cold (or too hot) makes some patients weak. Weather changes trigger episodes in some patients.
Many commonly prescribed medications may cause paralysis. These include muscle relaxants and beta-blockers, some types of tranquilizers, analgesics (pain killers), antihistamines, the puffers used to treat asthma attacks, some antibiotics and cough syrups. The eye drops used to dilate the pupil during eye exams have been reported to cause paralysis. Epinephrine or adrenaline , a drug routinely added to local anesthetics is used as a test to provoke attacks in HypoKPP, so obviously is a drug patients should avoid. Many patients report paralysis attacks occurring in the dentist's chair or in the hours following dental work, or after having a wound stitched or a mole removed.
Over the counter drugs can be dangerous and should be avoided if at all possible. If it is necessary to take something it's wise to begin with 1/4 of the recommended dose to gauge the effect on the muscles.
How can I determine what causes my attacks?
See How to Determine Episode Triggers
How do I avoid having attacks?
Learn what your triggers are and learn to avoid them. For some people this is enough. For others medication is necessary.
What tests are used to diagnose periodic paralysis?
There are a variety of tests used. If the patient presents with a spontaneous episode of significant weakness (generalized or localized) accompanied by a low level of potassium in the blood, and the weakness responds to potassium, given as a drink or IV, the diagnosis is relatively straightforward. At times diagnosis is not this easy, because the patient doesn't have an attack when the doctor or hospital is handy, and further tests are necessary. Many patients are aware that they may provoke an episode by eating a high carbohydrate meal, or by exercising, and the physician may choose to have them do that, in order to document a fall in potassium from their 'normal' level.
The subject of diagnosis is one which is somewhat complex, and is outside the scope of this discussion. However there is more information on this website about diagnostic tests and techniques. See Diagnosis in Hypokalemic Periodic Paralysis.
Where is the best place for treatment of HypoKPP?
The best place for treatment is almost always the patient's own family physician, if that physician is willing to read about HypoKPP 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 HypoKPP patient, and in these instances there is no time or opportunity to go to a far away specialist.
Who is doing research on HypoKPP?
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 HypoKPP?
Genetic testing is available, but it is not yet reliable enough to diagnose all HypoKPP patients. While a genetic test may be able to say you have HypoKPP, if the results of the test are negative that does NOT mean you do not have the disorder, as researchers know there are a number of variants which have yet to be identified. 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 many are still doing at this point). Make certain you will not be denied therapy by your physician or HMO should the test be negative!
Can HypoKPP be cured?
HypoKPP is cause by a mistake in the genetic 'blueprint' which was determined at the moment of conception. At present there is no cure. A person who has HypoKPP will have the disorder all their life, but there is treatment available.
What medications are prescribed for HypoKPP?
The carbonic anhydrase inhibitor 'Diamox' (acetazolomide) is often prescribed for HypoKPP patients. This medication helps keep the potassium from getting out of balance in the first place, by affecting the mechanism that pumps potassium from the blood into the cell. A similar drug called Daranide (diclorphenamide) is far more potent, and often works on patients who respond poorly to Diamox, or on patients who have been on Diamox many years and have become resistant to its effects. About 25% of patients do not respond to Diamox and must be put on other drugs.
Patients who take carbonic anhydrase inhibitors must be alert to potentially dangerous drug interactions as they slow the excretion of other drugs from the system. Avoid large doses of aspirin when taking Diamox or Daranide. Some other commonly used drugs to be cautious with when taking Diamox or Daranide include barbiturate medicines used for inducing sleep or treating seizures, the ephedrines (found in some over the counter asthma inhalers) the heart drug Mexitil (mexiletine), steroids and diuretic medications ('water pills'). Always discuss all other medications you are taking with your physician when starting a new drug.
Diuretics which cause the kidneys to 'spare' (or conserve) potassium are also used. Dyrenium and Aldactone (spironolactone) are in this family. Dyrenium is particularly useful as it causes the patient to excrete sodium as well as retain potassium, which is useful to patients who need to keep sodium intake low. Dyrenium (also sometimes called Triamterene) sometimes comes mixed with an agent which makes patients excrete potassium, so it's important to make certain the medication the HypoKPP patient is receiving contains no potassium-wasting diuretic.
Patients who are taking diuretics which cause the kidneys to conserve potassium should consult with their doctors before taking potassium supplements. Most people with HypoKPP still require potassium, even on diuretic therapy, but it should be carefully monitored. Those on Diamox or Daranide generally take some potassium to replace what is lost due to therapy itself.
Most patients with HypoKPP use potassium to abort developing episodes. Patients differ in their reactions to different forms of potassium but, as a rule, most people find that the effervescent potassium citrate or bicarbonate tablets which dissolve in water are the most effective and easiest on the stomach. Potassium chloride tablets are slow to dissolve and are hard on most people's stomachs, though some forms of potassium chloride capsules have coated granules of potassium which dissolve in the intestine and are much easier on the digestive system. These are preferred by many patients.
Will I be able to lead a normal life?
Most people with HypoKPP lead reasonably normal lives. Many cases of HypoKPP are mild, and even in those with severe and frequent episodes, medication and attention to diet and lifestyle issues can ease symptoms. There is no denying that more severely affected patients lead physically-compromised lives, especially patients with a long history of episodes. But many less-affected patients are quite active, and some engage in fairly strenuous sports. 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 HypoKPP?
Several of our families have affected members who have lived well into their 80s, in complete control of their mental faculties. Unless they have other health problems most are 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, or even impossible. 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 Hypokalemic Periodic Paralysis. For medical references see our Physician's Sheet on Hypokalemic Periodic Paralysis.