I believe the current thinking is that all genetic cases of EM are due to SCN9A mutations, so the other 85% of people with EM don't have the inherited form. I can't be certain that's accurate though. You can go on genetests.org to see what labs do the test. There are a few in the US, as of just this year.
Another issue is people like me, who seem to have EM secondary to a disorder that is genetic. Not everyone in my family who appear to have the underlying genetic disorder also have EM, but some of them do, even though we don't seem to have IEM (since some of the parents of EMers in my family do not have EM). There hasn't been enough research on the disorders that can cause secondary EM, especially the rare ones like mine. So, with 7,000 rare disorders out there it's impossible to determine much without the research.
A good genetics counselor could advise you. Maybe there are some at Barnes Hospital. Your doctor could refer you.
I'm awaiting the results of my genetic testing to see if I carry the SCN9A form. I think the 15% is only referring to the sub-type of EM that it occurs in. Basically, if you have the SCN9A form, you have primary EM (also called idiopathic EM) which developed before the age of 20 (the early-onset type). If you've no relatives with EM and you don't have primary early-onset EM, the chances that you have it are almost zero.
I've only been tested because there is a chance that another family member has it but it is masked by a different disease. I wanted to be tested to find out if there was any risk of it being inherited by my future nephews and nieces. It doesn't make any real difference to treatment at the moment, it just makes you very interesting to drug companies doing trials, as SCN9A EM patients are perfect for testing the next generation of pain-killers, which should work on all types of EM.
Sorry, forgot to say that they've not identified any other genes associated with EM yet. As Kentuckian said, with most EM caused by another conditon, teasing out the genes that are pre-disposing you to EM out from the genes causing or pre-disposiong you to the main condition will be very difficult. As EM is rare, it will need the coming cheap DNA sequencing before that will occur.
If you do have primary early-onset EM and you're planning a family, then talk to your doctor about genetic testing to see if you have an SCN9A mutation. Otherwise, inherited EM isn't something you need to be worried about
Thanks for the feedback. It's all very helpful, but still so confusing. I'm seeing a doctor on January 4th, so hopefully they can advise on what to do. I just fear that they still don't know enough about the disorder to give me the right information. We'll see. I'll check the sight mentioned for genetic tests. Surely I can find something somewhat close by.
K, You may already have seen this website, but in case you haven't, it's an important one for understanding Inherited Erythromelalgia (IEM) and SCN9A. You can print and share with your doctor if you think it would help.
http://www.ncbi.nlm.nih.gov/books/NBK1163/ Gene Reviews
I just sent my blood work to GeneDX. I do not have results back yet. You can call them to get a kit and then fed-ex it back. If you have certain kinds of insurance GeneDX limits your co-pay to $100.
Great link Kentuckian. I've printed off some great information.
Thanks Jama for the GeneDX link. The site states that there has to be a doctor referral, I'll definitely ask my doctor about this. I hope yours turns out well.
There is a form on their site you may want to bring to your Dr. appt. My doctor filled it out certain sections and then wrote a prescription for it. It could be something you could leave for you doctor and have him/her mail back to you. I included that paperwork when I sent the kit back. It was kind of confusing because it is not ordered like a typical blood test. I’ll try to come back and update when I get the results!
I had my DNA tested for the genetic mutation of the voltage-gated sodium channel (VGSC) Na(v)1.7 which is linked to human pain disorders. My blood was sent to Holland because this sort of testing isn't done in the UK. I was also told that because of this there is a 50% chance that my children will inherit my EM, but they also agreed that I would be the best person to help them deal with it if they do! My understanding is that EM can be genetic and does run in some families, although no-one else in my family has it.
Has anyone done this SNC2A genetic testing in Canada?