Rant away, it seems we've all come away from a consultation feeling less than happy with what they told us!

The only advice I can give is keep asking. It's tiring but honestly, it's the only avenue open to us.

Type of Myotonia: Becker's

Country: England

A couple more questions for anyone who can answer...

Is it common to have a mutation in the CLCN1 and SCN4A?

Is it common to have mutations that do not affect a person? In any gene?

Just wondering! :)

I'm still just starting to learn how this all works!

Country: USA

It would be extremely rare to have a mutatation on both genes. But it is not unusual to have missense mutations that have no significance clinically. I'll paste in a few paragraphs from Wikipedia (not always reliable, but in this case a good explanation!). Perhaps threonine and isoleucine are close enough structurally that they still activate the sodium ion channel when there is a substitution.

Jan

In genetics, a missense mutation (a type of nonsynonymous mutation) is a point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid (mutations that change an amino acid to a stop codon are considered nonsense mutations, rather than missense mutations). This can render the resulting protein nonfunctional. Such mutations are responsible for diseases such as Epidermolysis bullosa, sickle-cell disease, and SOD1 mediated ALS (Boillée 2006, p. 39).

For example, in sickle-cell disease, the 20th nucleotide of the gene for the beta chain of hemoglobin found on chromosome 11 is erroneously changed from the codon GAG (for glutamic acid) to GUG (which codes valine), so the 6th amino acid is incorrectly substituted (after the initial methionine amino acid is removed).

Not all missense mutations lead to appreciable protein changes. An amino acid may be replaced by an amino acid of very similar chemical properties, in which case, the protein may still function normally; this is termed a neutral, "quiet", or conservative mutation. Alternatively, the amino acid substitution could occur in a region of the protein which does not significantly affect the protein secondary structure or function. When an amino acid may be encoded by more than one codon (so-called "degenerate coding") a mutation in a codon may not produce any change in translation; this would be a synonymous mutation (a form of silent mutation) and not a missense mutation.

Type of Myotonia: Thomsen's MC

Country: US

Thanks so much Jan! I'm understanding more and more of this by the hour I think! :P

Country: USA

I got this response from one of the geneticists I contacted. I hope Dr. Lehmann-Horn will respond about the SCN4A mutation. I also heard back from the director of Athena Diagnostics' Genetics Lab who said he will investigate their database classification since this is a dominant mutation.

Jan

"Yes it would be called G230E. Independent of what has been found on genetic testing, if the family history shows an autosomal dominant pattern of inheritance then there is a 50% chance of passing it on to an offspring."

PS - I would strongly advise you to find another neurologist. His expertise is questionable and his behavior is atrocious!

Type of Myotonia: Thomsen's MC

Country: US

I'm so glad to be getting some answers on this, thank you so much! The first day I got my results I felt like it was a waste to even have had the test done! LOL. Why is it that Athena classifies this mutation only as recessive if it is also known to be dominant?

I do have a question about what the actual medical diagnosis would be on my records, would it be that I do not have the condition but am only a carrier? If so how would I go about getting it changed? My thoughts on having myself diagnosed at this point are that it would not just be for me, but also for any children I or my brother (who also has it) have. They would at least have a name for it and proof of what it is. Also they might only need a DNA test in order to be diagnosed themselves and not the EMG or any other painful testing.

I will also definitely be looking for another neurologist. It is a shame though because the one I was seeing was only a 15 min. drive from my home and any other is at least double that or even an hours drive to Pittsburgh. I picked up my entire chart from him yesterday though so I would have everything I needed when I find another. He has also already said he has never had a patient with MC, perhaps that is the reason for his complete lack of interest.

We should all also try to figure out who all of our ancestors are someday. I wonder how many of us may be distantly related! LOL

Country: USA