The cramp fasciculation syndrome some patients experience is caused by a potassium ion channelopathy. The symptoms which led to my diagnosis of CFS, however, are a direct result of the atypical myotonia congenita with which I've just been diagnosed. Treating the symptoms of my genetic disorder means treating the symptoms of CFS, as well as all those symptoms of mine that have, until now, defied categorization. For that reason, it's unlikely that I will continue to update this blog.
I'll keep the old material available. Feel free to link to or quote from this blog or the sister blog, Another Invisible Illness; I do ask, however, that you acknowledge the source and the author, Another Invisible.
Right now, I do not see myself keeping a blog about atypical myotonia congenita or sodium channel disorders. However, because there are so few patients with these disorders and research can be so hard to come by, I have created a forum for those who might be interested in supporting each other and sharing information. Although those who wish to participate in the more personal discussions are required to register, links to research and resources are available to the general public. I won't do a lot in the way of moderating the board; I plan to post links now and then and make sure postings and member names fall within the forum guidelines, but that's it.
I'd like to offer my sincere thanks to all of you who have followed the blog and wished me well. I hope that it has been, and will continue to be, helpful to others.
Best wishes to all of you,
Another Invisible
Tuesday, February 8, 2011
Diagnosis!
Yep, it's the sodium-channel form of myotonia congenita.
Dr. January was wonderful; he really took a lot of time to explain the genetic testing and how the laboratory databases work and such.
And he didn't misread my earlier report; it happened to be one of the few medical reports that somehow hadn't made it into my new file at the university hospital. He also asked if he could have a resident sit in, and he not only showed the new doctor what to look for in the physical testing, but how to listen to a patient's symptoms with an open mind. (The new doctor was listening carefully and respectfully; Dr. January was simply pointing out the importance of it and cautioning the doctor not to be dismissive when a physical cause is not immediately evident.)
Dr. January recommends trying a medication-only approach for now, as opposed to making drastic dietary changes. I told my husband that I'd been hoping I'd be ordered to stay away from Big Macs, because I might be able to do it under doctor's orders, but I certainly won't listen to myself.
Dr. January was wonderful; he really took a lot of time to explain the genetic testing and how the laboratory databases work and such.
And he didn't misread my earlier report; it happened to be one of the few medical reports that somehow hadn't made it into my new file at the university hospital. He also asked if he could have a resident sit in, and he not only showed the new doctor what to look for in the physical testing, but how to listen to a patient's symptoms with an open mind. (The new doctor was listening carefully and respectfully; Dr. January was simply pointing out the importance of it and cautioning the doctor not to be dismissive when a physical cause is not immediately evident.)
Dr. January recommends trying a medication-only approach for now, as opposed to making drastic dietary changes. I told my husband that I'd been hoping I'd be ordered to stay away from Big Macs, because I might be able to do it under doctor's orders, but I certainly won't listen to myself.
Tuesday, February 1, 2011
The Atypical Myotonia Congenita/Potassium-Aggravated Myotonia Connection
According to this 2003 GeneReviews article by Doctors Jurkat-Rott and Lehmann-Horn about hyperkalemic periodic paralysis (under "Genetically Related [Allelic] Disorders"), atypical myotonia congenita is the form of potassium-aggravated myotonia known as acetazolamide-responsive myotonia. Two other forms of potassium-aggravated myotonia are myotonia fluctuans and myotonia permanens.
The abstract for the paper cited in GeneReviews, "Sodium Channel Mutations in Acetazolamide-Responsive Myotonia Congenita, Paramyotonia Congenita, and Hyperkalemic Periodic Paralysis," by Ptacek, Tawil, et al., can be found here.
The abstract for the paper cited in GeneReviews, "Sodium Channel Mutations in Acetazolamide-Responsive Myotonia Congenita, Paramyotonia Congenita, and Hyperkalemic Periodic Paralysis," by Ptacek, Tawil, et al., can be found here.
Friday, January 28, 2011
I'm a Little a Lot Confused
I can't quite be certain, but it seems as though the researchers who've written about an atypical, SCN4A-related form of myotonia congenita are referring to the disorder that other researchers have called "sodium-channel myotonia," which I've read about before under its alternate name, potassium-aggravated myotonia. In fact, I've not only read about it before, I emailed my husband with a link a couple of days before my appointment with Dr. January, saying, "This is my guess."
However, I'm still really confused. I looked more closely at Dr. January's report, and he says, "I suspect myotonia congenita associated with a chloride channel alteration, but there are other considerations." Okay, SCN4A is a sodium channel. CLCN1 is a chloride channel. I just don't have a chloride channel mutation. I don't. On the other hand, it's now beyond doubt that I do have a sodium channel mutation. It's true that I'm not a doctor of any sort, but this isn't up for debate. Laypeople can understand definitions; doctors don't get to rewrite them without a (generally) hard-to-get consensus.
Believe me, I'm thrilled that an expert is ready to put a name to this. But I do find the discrepancies in the language disheartening. I don't know if the doctor misspoke when dictating his report, or if he misread the report from Athena.
Hopefully, the EMG results in a couple of weeks will be clear cut and leave no room for confusion. I'm trying to figure out just how to ask about this diplomatically if they do, or if the language still leaves me confused.
However, I'm still really confused. I looked more closely at Dr. January's report, and he says, "I suspect myotonia congenita associated with a chloride channel alteration, but there are other considerations." Okay, SCN4A is a sodium channel. CLCN1 is a chloride channel. I just don't have a chloride channel mutation. I don't. On the other hand, it's now beyond doubt that I do have a sodium channel mutation. It's true that I'm not a doctor of any sort, but this isn't up for debate. Laypeople can understand definitions; doctors don't get to rewrite them without a (generally) hard-to-get consensus.
Believe me, I'm thrilled that an expert is ready to put a name to this. But I do find the discrepancies in the language disheartening. I don't know if the doctor misspoke when dictating his report, or if he misread the report from Athena.
Hopefully, the EMG results in a couple of weeks will be clear cut and leave no room for confusion. I'm trying to figure out just how to ask about this diplomatically if they do, or if the language still leaves me confused.
Thursday, January 27, 2011
Links to Information about Atypical (SCN4A-Related) Myotonia Congenita
From the NIH National Center for Biotechnology Information site, about halfway down the page, under "Mapping":
In a family with acetazolamide-responsive atypical myotonia congenita, Ptacek et al. (1992) found linkage to SCN4A; maximum lod score = 3.56 to 4.19 at theta = 0.0, depending on assumed penetrance varying from 0.7 to 1.0.
The abstract for the Ptacek, et al., study, "Linkage of Atypical Myotonia Congenita to a Sodium Channel Locus," is here.
In a family with acetazolamide-responsive atypical myotonia congenita, Ptacek et al. (1992) found linkage to SCN4A; maximum lod score = 3.56 to 4.19 at theta = 0.0, depending on assumed penetrance varying from 0.7 to 1.0.
The abstract for the Ptacek, et al., study, "Linkage of Atypical Myotonia Congenita to a Sodium Channel Locus," is here.
Tuesday, January 25, 2011
Part of Conversation with Dr. January at First Appointment
Me (kind of tearily): Ever since I got the genetic testing back, I've been so worried that I've given my son, this active, hiking-all-the-time kid, some crappy disease.
Him (kindly, but very firmly): Hold it right there. You didn't give him anything. If he's smart and good looking, you didn't give him that, and you didn't give him this. It's the luck of the draw. If you have some kind of original sin or guilt, you need to take those issues somewhere else to deal with.
It was exactly what I needed to hear, and my husband and I burst out laughing.
Him (kindly, but very firmly): Hold it right there. You didn't give him anything. If he's smart and good looking, you didn't give him that, and you didn't give him this. It's the luck of the draw. If you have some kind of original sin or guilt, you need to take those issues somewhere else to deal with.
It was exactly what I needed to hear, and my husband and I burst out laughing.
Monday, January 24, 2011
A Suspect! Myotonia Congenita, We Have a Few Questions for You.
The appointment today was wonderful. Dr. January at the University of Pennsylvania took me very seriously and believes he knows what the problem is. The physical exam he gave was the most thorough I've ever had, as was the medical history he took.
He's ordered a few blood tests, which he expects to be negative (and, in fact, I've had them more than once before and they have always been negative). He also ordered an EMG that he will perform (remember, this is at a premier EMG lab), and I'll have that in a couple of weeks.
The suspected culprit is myotonia congenita. [Edit: I had this wrong when I first wrote up this entry; I thought the doctor was talking about paramyotonia congenita, mostly because the gene almost always associated with myotonia congenita is CLCN1; SCN4A is associated with paramyotonia congenita. However, I just got a copy of the report today; right there in black and white, Dr. January says he suspects "myotonia congenita." I did a little digging and found a couple of studies saying atypical cases of myotonia congenita can be caused by mutations in SCN4A.]
I was very active as a child, teen, and young adult, but Dr. January didn't seem to be surprised or bothered by this. (I do recall the sensation of muscle tightness even as a child, but it didn't slow me down, and I didn't know it might be abnormal.)
The doctor also said that the symptoms of myotonia congenita can be managed, and that there are better drugs available to treat the muscle tightness than any I have tried.
The news that this disease can be managed is the best news of all. It was a tremendous relief to hear that even if my son is at risk for this disease, his quality of life will not necessarily be compromised even if he develops it.
I'll let you know the results of the EMG in a couple of weeks; I'm expecting to see something (after all, I've already had one abnormal EMG), but I'm not sure what. I also don't know if the kind of activity seen will make a difference diagnostically.
He's ordered a few blood tests, which he expects to be negative (and, in fact, I've had them more than once before and they have always been negative). He also ordered an EMG that he will perform (remember, this is at a premier EMG lab), and I'll have that in a couple of weeks.
The suspected culprit is myotonia congenita. [Edit: I had this wrong when I first wrote up this entry; I thought the doctor was talking about paramyotonia congenita, mostly because the gene almost always associated with myotonia congenita is CLCN1; SCN4A is associated with paramyotonia congenita. However, I just got a copy of the report today; right there in black and white, Dr. January says he suspects "myotonia congenita." I did a little digging and found a couple of studies saying atypical cases of myotonia congenita can be caused by mutations in SCN4A.]
I was very active as a child, teen, and young adult, but Dr. January didn't seem to be surprised or bothered by this. (I do recall the sensation of muscle tightness even as a child, but it didn't slow me down, and I didn't know it might be abnormal.)
The doctor also said that the symptoms of myotonia congenita can be managed, and that there are better drugs available to treat the muscle tightness than any I have tried.
The news that this disease can be managed is the best news of all. It was a tremendous relief to hear that even if my son is at risk for this disease, his quality of life will not necessarily be compromised even if he develops it.
I'll let you know the results of the EMG in a couple of weeks; I'm expecting to see something (after all, I've already had one abnormal EMG), but I'm not sure what. I also don't know if the kind of activity seen will make a difference diagnostically.
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