Gene Testing Primarily EM



Hi, we’ve been on this road of EM for a little over five years. My daughter has it in her face, ears, hands, feet, and legs. We have been to Mayo Clinic in Arizona and Minnesota and she is received an official diagnosis. She is tried medication after medication after medication after medication nothing seems to affect her. We did get back some genetic test showing that she had a mutation in the SCRN9. A little further testing also showed that she inherited it from me as I have the same mutation. I exhibit a little of the symptoms and have all my life. My daughter has them to an extreme where it is life debilitating. Now that we know it is primary I’m wondering if anyone else who has it as a primary has tried any medications that has worked. I appreciate and take any and all advice. God Bless, Bonnie

Sodium channel blockers, namely, mexiletine are the go to treatment for primary EM. Lidocaine infusions (mexiletine analog) are also a common treatment for primary EM.

Thank you! Those are great suggestions and we have tried them all but lidocaine infused. I will ask pain management doctor about that. Have a great day.

There are a few categories of sodium channel blockers that can be used for primary EM (lidocaine, mexiletine, carbamazepine, oxocarbazepine). Sometimes mexiletine can take a few weeks or a couple of months to effectively reduce the sympathetic flow associated with EM. Here is a good cumulative review paper that I posted a year ago or so that covers everything. Lidocaine infusions have shown to be extremely effective in cases of primary EM in young patients with the possibility of complete remission, it is something to maybe look into (I’m surprised mayo clinic didn’t mention this). I must also add that the two successfully treated cases I’ve read about were done with continuous inpatient infusions over the course of a few days, while outpatient weekly infusions aren’t mentioned (they certainly could be successful, cases just aren’t coming to mind right now.)

Review Article

Primary EM cases treated with continous IV lidocaine

What dose of mexiletine did she try? I agree w/ joeshmoe it might take a while to notice effects, but i think some people might give up when higher doses might have been helpful. My first trial at 300 mg a couple yrs ago had no effect. The past 4 months I have been slowly incrementing (under derm’s guidance) to max tolerated dose. I was told I could go up to 900 mg or 1200 mg. Currently at 750 mg and (other than opioids) is the first oral medication that has helped my afternoon + night flares. The only side effect I have is some insomnia.

I am also on zonisamide which is an anti-seizure sodium channel blocker. I am only on 100 mg because higher doses for me affect thinking ability. This helps too.

I am very grateful I tried mexiletine again, at a slow + steady rampup. I have also tried a long lidocaine infusion (Stanford pain) and for me the analgesia did not stick.

(I don’t have any known mutations, but a neurologist told me once that really that doesn’t change treatment, that in SFN, the sodium channels are messed up either way … at least what I understood.)

Take care.

She tried 10 mg but because she has extremely low blood pressure she was not able to continue. She became dizzy disoriented and was not able to function. I’m so glad that it worked for you this is a crazy disorder where one thing work for one person and not for another.

She is lucky that she has tested positive for the primary form though as it is a step forward in figuring it all out. 10mg is not nearly enough at all in my opinion. I take 200mg 2x daily and it took about a month to see results. I am now symptom free, not sure whether it is from the medications I take or the capsaicin cream but I did learn in the process that it can take time before results are seen.

I think you are probably mistaken on that dosing. Mexiletine is manufactured in capsules of 150 mg, 200 mg and 250 mg. Unless your daughter was having mexiletine created in specialized capsules by a compounding pharmacy, she was taking one of the 3 aforementioned doses.

That is disappointing. I wonder if she were to take something for the low blood pressure, she might be able to tolerate mexiletine. I am not a doctor and I’m not even sure I’m “allowed” to write things like that on this forum.

There are some mutations / polymorphisms in SCN9A that respond exquisitely to mexiletine - so I wonder if your daughter has one of these. (There are also some that respond better to carbamazepine.) Did you see a geneticist?

A super slow titration might also help her tolerate it better. But, 10 mg is as slow as you can get.