Is most cases of EM unknown or secondary?

Hey :slight_smile:

I am a bit confused. While I did some research on EM on google, I found out that you have two types, secondary or primary EM, and most of the pages sais that " for most people with erythromelalgia, the cause is unknown, while others sais that secondary is the most common form?

What is secondary then? Does that also mean that a case is unkown?

In the norwegian sites it sais that “more then 90% of the cases of EM have a unkown reason”. How can the secondary form be more common then?

Primary EM is caused by sodium channel mutations which can be tested for. These account for roughly 10-15% of cases. The remainder is secondary causes, meaning that the EM is due to a non-genetic problem. That can be cancer, a rampant nervous system after injury, high blood pressure, a dysfunctional endothelium, or microvasculature changes among many things. THAT is why EM is so hard to treat, it can be secondary for numerous things.


But why does it then say that more then 90% of the EM-cases have a unkown cause, if most of the cases are secondary?

The two categories overlap. If a case isn’t primary it is secondary by default. However, the cause of secondary cases is often unknown.

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From what I know about and have read about EM. I strongly disagree with this statement. Unless someone has decided to say primary EM is only genetic which I have never heard from a study or competent authority.

Here is what EM primary and secondary has traditionally meant when they were discussed. First EM is a pain and heat flare that happens which is a burning and painful situation that responds to heat with flares and pain and is resolved by chilling of the feet. The feet find relief from cooling via water immersion, ice packs (which both can damage tissue) and elevating the feet. The hallmark symptoms of EM is you have burning and pain in your feet which is very painful but the level of pain may vary when they are warm and environmental relief comes from cooling of the feet and resting the feet often elevating them. There is an autonomic response which almost every patient with EM has with is a swelling and pooling of blood. Now this being the case in a more technical point of view EM falls into a classification of diseases not as a disease but as a syndrome with often “unknown” causes. The cause is often a long drawn out affair to find out what kind of damage to the nerves, autonomic system or vascular system which may be causing it. But it’s hallmark for a classical definition of “mitchell’s disease” is that it’s almost always nerve damage related in some way. Which mean the nerves are either “damaged” like dead or malfunctioning, perhaps overactive, perhaps an EM flare like condition can happen with weird strange nerve related diseases with “overactive Glial cell functions like CRPS type 2” patients who may have EM like flares which occur for up to one year and sometimes longer. When you feet are flaring and burning unexpectedly, you will say I’m having a burning foot and pain problem. But if you look up hot feet and “hot feet” relief from flares you will find many say they can sell you vitamins or something to help cure or deal with your “burning foot” flare problem which is related to diabetic foot conditions. In the case of many diseases and problems people get burning or painful feet. There are something like 800 conditions which have a side effect, just one of many which include burning or pain in the feet. So in those cases people are getting “flares” and they may have the flare symptoms resolve when the cause of the SYNDROME, which is EM is discovered. My feet are hot and burning, perhaps due to an allergy, perhaps due to fungus, perhaps due to lack of vitamin B5 in a Japanese prison camp, perhaps due to some other problem related to my nerves, perhaps due to the autonomic nervous system which is sending blood to the feet because of lack of sensory feedback from nerves which are not functioning (small fiber or large fiber neuropathy which means nerve damage), perhaps as a side effect of cancer drugs which affect my nerves and cause weird reactions, perhaps due a mixture of those things happening. Perhaps I’m getting flares from a progressive diabetic condition. And lastly perhaps to a sodium channel genetic defect. About 6 years ago I spoke to a person at Stanford(?) university, was it standford, I forgot but they were the leading researchers working on the Genetic NAV1.7 cause of burning foot syndrome which the person who I talked to said affected “only 30 familiar groups world wide”. They only had 30 families which they had identified that had the EM as a result of a defective gene. Also people who have the defected gene don’t all develop EM, about 20 percent of them do.

Statistics from an old study from the Mayo clinic said EM affects about 1.3 out of a 100,000 people which means in the USA it’s quite rare and affects about 5000 people. Those 5,000 people don’t have EM because they have a genetic gene variation in the Sodium NAV 1.7 channel.

Some have EM due to a pinched nerve or nerve entrapment. So there are a lot of possible causes. When you don’t have another disease that is known and is a cause of EM, you will often be diagnosed with “burning foot syndrome” perhaps after six months or two years of seeing doctors. They will try to rule out other causes. Flares from CRPS type 2 are not tied to heat as far as I can tell. That disease just seems to randomly cause hell for it’s suffering patients. When it’s rare and seems to come from nowhere or no other known and easily to identify disease, they call it “primary” because it’s the only primary symptom you have and the cause it unknown. So most people who have EM have it as a primary symptom with an unknown cause. That is those who are DIAGNOSED with EM. But those who have burning feet or flares. Well supposedly millions of people with diabetic conditions have foot pain flares as their small fiber nerve damage from sugar destruction of their small capillaries kills off their nerves in their extremities. So potentially millions of diabetics have burning foot like flares, and you could argue that they have a hot flare, so they have burning foot syndrome, but it’s a secondary condition and their condition is due to nerve damage in the feet. What happens with the diabetic is their feet become numb as the nerves die, so their body may respond the same way or in some bad way and they may have horrible looking, damaged and swollen feet, but they don’t feel them because their feet are numb from further nerve damage.

Some people have damage to their nerves others to their autonomic nervious system. I guess you could say it’s all connected. If your system is automatically responding to a numbed foot where it thinks the nerve is cut or almost all the signal is lost, the body will automatically respond and send more blood to the affected limb, because it thinks a bad injury has happened and it will cause blood to flow to the foot.

With early suffering with Mitchell’s disease soldiers in the Civil war had feet that were burning, but there was nothing wrong with their feet. The damage was elsewhere in the nerves. Burning Foot syndrome is kind of like phantom limb syndrome as well, because the feeling of damage and result response with blood flow can go to the feet when there is nothing wrong with the feet. Some may have swelling feet, edema because of poor circulation problems and they may have a bad vascular condition so if you have hot and swelling feet you may have vascular flow studies done. But the average burning foot EM flare patient doesn’t have a problem with their circulation which is impeding the return of blood. They just have a circulatory system that is pumping to much blood down there and causing the blood vessels to dilate sending more blood to the limb.

People also can have sharp nerve related pains, like their toenails are being pulled out and electrical shock feelings during the onset of a bad case of EM. They may have symptoms change over time. People also have a body that can be tuned perhaps from their response but likely not from that, which causes their body to go into a seesaw like pattern of reacting to a flare with cold feet and then the nerves respond to warm up the feet more in response to the environmental chilling. So the environmental treatments can be looked down on by professionals as causing problems with chill and warming cycles. In some cases perhaps that is happening. Many patients will not listen to the doctors and will have to chill because often the only thing to resolve a flare for a patient is environmental chilling.

When you’re nerves are damaged the body may respond in some unknown way as far as a layman would be concerned and it may even confuse the doctors. One can have more than one condition when they are old and these different conditions will cause different symptoms and side effects from different drugs. And different conditions may even cause your body to react differently. Some medications which may cause raynaud’s disease or side effects from drug interactions like Seritonin sickness could trigger a cold feeling which is opposite of EM. Some drugs if taken together may push EM symptoms toward raynaud’s like symptoms. As if the suffering person is on a tight rope and their feet may become numb and cold from medication. Environmental chilling may do the same.

Well this is just some of the stuff I’ve heard. Often it’s a permanent nerve damage condition that causes the problem. Something in the autonomic system may be reacting to unknown damage. My mother developed EM from taking Risperdal. Some have developed it from taking Amitriptyline. In both cases (these are rare cases with the Risperdal or Amitriptyline) the nerve damage is done and it’s likely permanent and the body is not responding with flares which can be almost constant or if you’re lucky occasional.

My sister had burning scalp and face syndrome written down by one doctor who saw her strange side effects affecting her face and scalp. It was some kind of side effect from other problems and they never totally figured it out, but also she had different medications for other conditions which could perhaps help resolve her “burning EM like symptom” but her moving out of an apartment also seemed to help her. So in her case when I heard of some of her symptoms I thought maybe it’s genetic, but we’ve never tested for it.

It’s also important to realize with rare diseases doctors might not really know what is going on but may make interesting and strange comments like “the drug didn’t cause it” it “triggered the genetic factors in you which cold cause it”. These words and theories put out especially for the rare victim of drug induced EM seem more like cover for the drug industry than a good explanation. But also they may make comments based on statistical rarity. EM is rare, but considering that EM has maybe 5000 people who suffer for it, it’s rare compared to “secondary flares” for example diabetic burning feet happens all the time, but is offset by numbness. If you are like some of the members of the board, you will find many have more than one disease often nerve related and EM came with the mix. Poly Neuropathy can cause EM and it’s simply “more than one type” or “poly” Nerve damage.

Damage anywhere from the DSG or dorsal root Ganglia to the foot can cause burning foot syndrome. So neurologically any damage along the pathway can be the cause. Nerve studies are often done by Neurologists to try to isolate the exact type of nerve problem you have which may cause the EM. Even when they find it, that doesn’t mean they find a cure for the EM, they just narrow down the cause.

Of those who are diagnosed with EM, probably most of them are primary EM patients, but there are many secondary EM flares and those who get them may never come to an EM group or just consider it a pain flare and be treated for other diseases. If the other treatment can help the other disease the EM like flare condition is resolved. It’s a syndrome or “condition” not a specific disease. It’s often something that happens to the foot but it’s caused by something other than an injury to the foot. It’s one of the rare conditions that prove pain can be from damage somewhere else in the body.

If you have a flare from diabetic condition and even have them for a year or so, they may respond to medication differently or finally stop. Those are often not considered EM symptoms but just a pain flare from diabetic conditions. Some mass remedies are marketed to those who suffer from flares which are secondary and they don’t help people with “primary EM” meaning ONLY BURNING FEET with no other easy to find causes. It just appears as the primary symptom, out of nowhere and it’s a mystery, so it’s lumped into the EM category. If it’s not resolved by cold water chilling it’s probably not EM. If it cannot be caused by getting your feet warm then it’s probably not EM. It can be an EM like flare, but it’s not EM. Secondary EM is a blessing, if the cause can be solved, the EM will go away. I have my own theory, about EM as far as burning only EM cases, and mixed symptoms or secondary flares from destructive nerve damage. I think many of the medications which work with people with mixed symptoms don’t work on the “burning only” variety which to me is a pure primary EM. I may be wrong and I’m not a medical professional. I’m just basing that on very little samples of what I’ve read in the past on these forums. Not being a wide spread disease and without many studies not much can be deduced and inferred about EM. It’s kind of a rare catch phrase or “syndrome”. It’s a set of symptoms rather than a pure measurable diagnostic as far as “knowing for sure” what caused it. In a sense secondary EM isn’t even EM at all. Only primary EM is EM because the cause is unknown.

I think some have said genetic EM is primary because they want to emphasize the progress of genetic research, but that doesn’t seem to be the case at least historically or diagnostically as I have read about it.

The people studying EM didn’t say to me over the phone, your mom does not have EM, because it’s likely not genetic. They said she likelyh didn’t have their form of genetic EM. They said she probably has EM from drugs damaging her nerves. Doctors who looked at photos and read the symptoms of my mom’s condition had a few conclusions which were universal it seems. 1. it’s from nerve damage. 2. It’s permanent damage and won’t be cured.

If you have a lot of other conditions doctors might guess that they could be causing your primary EM flares and they may be treated and that treatment may resolve those other symptoms but you still may have flares because you have primary (unknown cause or generally nerve related or auto-immune related) EM.

I didn’t read all of that just because it was too long but that statement is incorrect.

Primary EM is in fact documented in many journals and is medically termed as having a mutation in the SCN9A sodium channel gene and can be tested for easily via a blood test. This is the type that responds most strongly to sodium channel blockers like mexiletine or lidocaine.

Secondary is anything else, including nerve damage, that could lead to the autonomic and microvasculature changes that accompany flares.

Idiopathic EM is EM that is secondary but a cause has not been determined yet.


The GARD (Genetic and Rare Disease) Information Center of the National Institutes of Health, a division of the US Department of Health and Human Services, says the following about erythromelalgia:


Erythromelalgia (EM) is a rare condition characterized by episodes of burning pain, warmth, swelling and redness in parts of the body, particularly the hands and feet. This condition may occur spontaneously (primary EM) or secondary to neurological diseases, autoimmune diseases, or myeloproliferative disorders (secondary EM). Episodes may be triggered by increased body temperature, alcohol, and eating spicy foods. About 15% of cases are caused by mutations in the SCN9A gene and are inherited in an autosomal dominant manner. Other cases may be caused by unidentified genes or by non-genetic factors. Treatment depends on the underlying cause and may include topical and/or oral medications. In some cases, the condition goes away without treatment.[1][2]

Last updated: 8/4/2016


About 15% of cases of erythromelalgia are caused by mutations in the SCN9A gene. The SCN9A gene gives instructions for making part of a sodium channel which carries sodium into cells and helps them make and transmit electrical signals. These sodium channels are found in nerve cells that transmit pain signals to the spine and brain. Mutations that cause erythromelalgia cause increased transmission of pain signals, leading to the signs and symptoms of the condition. In some of these cases, an affected individual inherits the mutation from an affected parent. In other cases, a new mutation occurs for the first time in an individual with no history of the condition in the family.[2]

In the remainder of cases, the exact underlying cause is not currently known. Evidence suggests that it results from abnormalities in the normal narrowing and widening of certain blood vessels, leading to abnormalities in blood flow to the hands and feet. There may be a variety of non-genetic causes, or mutations in other genes that have not yet been identified.[3]

Last updated: 8/4/2016

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The only dispute I have with your statement is with regard to idiopathic EM, which by definition can’t be categorized as primary or secondary. Idiopathic EM may arise from an unknown secondary cause, mutations in genes that have not yet been identified, or a combination of both.

That is very true. There could very well be genetic causes that aren’t found yet. Hopefully gene sequencing will help expedite that process in the near future.

Additionally, since the diseases and disorders EM can be secondary to are much more common than EM itself, it’s also possible all secondary cases have an as yet unidentified genetic or epigenetic cause that is triggered by the underlying illness. At this point the most salient reason for the separation of primary and secondary erythromelalgia cases is treatment approach. Treating the underlying illness in secondary cases tends to also help treat the erythromelalgia. However, too little is known about how secondary cases arise to preclude a genetic cause.

Also I just wanted to know if it was possible for primary EM just to randomly show up in a healthy 21 year old? If it’s only primary other than being annoying and uncomfortable does it pose any serious health risks?

What does this meant then? Here it sais 80% of the cases are primary :slight_smile: