Test Result Details, Etc.

Sequence variant in the SCN4A gene at transition A > G, nucleotide position IVS19+10.

From the report: "Since this type of sequence variant is similar to those observed in disease-associated mutations and benign polymorphisms, the nature of the variation prohibits definitive interpretation."

Forty other variants in the SCN4A gene have been linked to a variety of muscular disorders. Also, disease-associated mutations of the gene have a high penetrance, which means that carriers of the mutations have a high likelihood of developing the associated diseases.

But again, the report basically says that there isn't enough known about the variant I have to determine whether it is associated with disease or not.

Soooo . . . 40 other variants in this gene are known to cause muscle disease, I'm sitting here with the same darn symptoms, and the lab can't say, "Yes, this is a problem"?

However, the lab does say that "careful reconciliation of this molecular data with this individual's clinical and family history is highly recommended. Athena strongly recommends genetic counseling for this individual and his or her family members, and consideration of testing for family members."

SCN4A gene variants can be both inherited and sporadic. Inherited forms are autosomal dominant, which means a child who has just one parent with the defective gene has a 50% chance of having it as well. My symptoms go back many years; I may have had mild symptoms even before I had my son.

For more information about the gene itself and the kinds of problems its mutations can cause, check out the SCN4A page at the National Institutes of Health US National Library of Medicine.

Test Oddity

I called today to get the results of the Athena Complete Myotonia Workup that the last neurologist ordered. (He originally ordered it instead of the VGKC antibodies test, but then added the VGKC to the order.)

All of the standard components that indicate myotonia were normal. However (boy, it feels good to have a "however" - it feels good to have anything resembling a clue at this point), there was one component of the test that was strange. One of my sodium channel results was odd. Evidently, there is an aberration in my DNA sequencing relating to this one sodium channel.

The neurologist who left me the message with my results (who is filling in right now for the one who ordered the tests) said that the channel in question was not known to cause problems and was not commonly tested [update 11/04/10: clearly, I misunderstood this bit; the gene, SCN4A, is sequenced because it has many variants that are known to cause problems; this variant is one whose significance is unknown], and that the clinical significance of this result is unknown. But that sounds a whole lot better to me than "clinically insignificant," which seems to be the go-to phrase for test result hiccups.

I do have to wonder why this component was even part of the test if this sodium channel is not known to cause problems and no one knows what aberrant results might mean. In other words, why test for something that means nothing? Surely it must mean something to someone.

I missed the neurologist's call by about five minutes, so I called back immediately and left a message asking him to call me back. Hasn't happened yet, so I'll post when I know more.