Is Gamstorp Disease?
Gamstorp disease is an extremely rare genetic condition that
causes you to have episodes of muscle weakness or temporary paralysis. The
disease is known by many names, including hyperkalemic periodic paralysis. It’s
an inherited disease, and people can carry and pass on the defective gene
without ever experiencing symptoms. One in 250,000 people have
Although there’s no cure for Gamstorp disease, most people
who have it can live fairly normal, active lives. Doctors know many of the
causes for the paralytic episodes and can usually help limit the disease’s
effects by guiding people with this disease to avoid certain identified triggers.
Are the Symptoms of Gamstorp Disease?
Gamstorp disease causes unique symptoms, including:
- severe weakness of a limb
- partial paralysis
- irregular heartbeats
- skipped heartbeats
- muscle stiffness
- permanent weakness
Paralytic episodes are short and may end after a few
minutes. Even when you have a longer episode, you should typically recover
fully within two hours of the symptoms starting. However, episodes often occur
suddenly. You might find that you don’t have sufficient warning to find a safe
place to wait out an episode. For this reason, injuries from falls are common.
Episodes typically begin in infancy or early childhood. For
most people, the frequency of the episodes increases through the adolescent
years and into their mid-20s. As you approach your 30s, the attacks become less
frequent. For some people, they disappear altogether.
One of the symptoms of Gamstorp disease is myotonia. If you
have this symptom, some of your muscle groups can become temporarily rigid and
difficult to move. This can be very painful. However, some people don’t feel
any discomfort during an episode.
Because of constant contractions, the muscles affected by
myotonia often look well-defined and strong, but you might find you can only
exert little or no force using these muscles. Myotonia causes permanent damage
in many cases. Some people with Gamstorp disease eventually use wheelchairs due
to deterioration of their leg muscles. Treatment can often prevent or reverse
progressive muscle weakness.
Are the Causes of Gamstorp Disease?
Gamstorp disease is the result of a mutation, or alteration,
in a gene called “SCN4A.” This mutation produces sodium channels, or
microscopic openings through which sodium and potassium move through your
cells. Electrical currents produced by different sodium and potassium molecules
passing through cell membranes control muscle movement.
In Gamstorp disease, these channels have physical
abnormalities that cause potassium to gather on one side of the cell membrane
and build up in the blood. This prevents the needed electrical current from
forming and causes you to become unable to move the affected muscle.
Who Is at Risk for Gamstorp Disease?
Gamstorp disease is an inherited disease, and it’s autosomal
dominant. This means that you only need to have one copy of the mutated gene to
develop the disease. There’s a 50 percent chance you have the gene if one of
your parents is a carrier. However, some people who have the gene never develop
Is Gamstorp Disease Diagnosed?
To diagnose Gamstorp disease, your doctor will first rule
out adrenal disorders such as Addison’s disease, which occurs when your adrenal
glands don’t produce enough of the hormones cortisol and aldosterone. They’ll
also attempt to rule out genetic kidney diseases that can cause low potassium
Once they rule out these adrenal disorders and inherited
kidney diseases, your doctor can confirm if it’s Gamstorp disease through blood
tests, DNA analysis, or by evaluating your serum electrolyte and potassium
To evaluate these levels, your doctor may have you do tests
involving moderate exercise followed by rest to see how your potassium levels
change. Someone with Gamstorp disease will see high potassium levels during
exercise that reduce during rest and rise again 20
minutes after stopping the exercise.
Preparing to See Your Doctor
If you think you may have Gamstorp disease, it may help to
keep a diary tracking your strength levels throughout each day. You should keep
notes about your activities and diet on those days to help determine your
triggers. You should also bring any information you can gather about whether or
not you have a family history of the disease.
What Are the Treatments for
The treatment is based on the severity and frequency of your
episodes. Medications and supplements work well for many people who have this
disease. Avoiding certain triggers works well for others.
Most people have to rely on medication to control paralytic
attacks. One of the more commonly prescribed medications is acetazolamide
(Diamox), which is commonly used to control seizures. Your doctor may prescribe
diuretics to limit the potassium levels in the blood. People with myotonia as a
result of the disease can be treated using low doses of drugs such as mexiletine (Mexitil)
(Paxil), which help stabilize severe muscle spasms.
People who experience mild or infrequent episodes can
sometimes curb a paralytic attack without the use of medication. You can add mineral
supplements, such as calcium gluconate, to a sweet beverage to stop a mild
episode. Drinking a glass of tonic water or sucking on a piece of hard candy at
the first signs of a paralytic episode may help as well.
Coping with Gamstorp Disease
Potassium-rich foods or even certain behaviors can trigger
episodes. Too much potassium in the bloodstream will cause muscle weakness even
in people who don’t have Gamstorp disease. However, those with the disease may
react to very slight changes in potassium levels that wouldn’t affect someone
who doesn’t have Gamstorp disease.
Common triggers include:
- fruits high in potassium, such as bananas,
apricots, and raisins
- potassium-rich vegetables such as spinach,
potatoes, broccoli, and cauliflower
- lentils, beans, and nuts
- long periods of rest or inactivity
- going too long without eating
- extreme cold
- extreme heat
Not everyone with Gamstorp disease will have the same
triggers. Talk to your doctor and try
recording your activities and diet in a diary to help determine your specific triggers.
Is the Long-Term Outlook?
You can moderate the effects of the condition by carefully
managing your risk factors. Aging reduces the frequency of the episodes. It’s important to talk to your doctor about
foods and activities that might be causing your episodes. Because
Gamstorp disease is hereditary, you can’t prevent it. However, avoiding the
triggers that cause the paralytic episodes can limit the disease’s effects.