TJ22,
I am a senior Cell and Molecular Biology student (BS) with a strong background in genetics. Here is what I understand your results to mean, with a little bit of background in terms so when you hear them again, you will know what they mean. Please remember, although the terms I define I know to be correct, my interpretation of the actual results may not be, as I am not a geneticist with a PhD.
A heterogeneous means that one allele, or gene, is not the same as the other on the opposite chromosome at the same location. Having a heterogeneous deletion means that your child has one chromosome that has a deletion, while the other chromosome does not. Now, DNA has two parts to it: exons and introns. Exons are the portions of DNA that code for proteins. Introns are the sequences between the exons that don't really code for anything, although they can play a role in gene expression. When your DNA is read and RNA (RNA is like the messenger that takes a copy of the genetic code to the factory where proteins are made and assembled) is formed, the introns get "snipped" out of the RNA so that the exons are in one continuous line. This allows for the correct formation of various proteins that the body needs to function.
Now, jumping back to introns for a moment. I stated that they can play a role in gene expression. Some CF mutations only will be expressed if there is a certain number of T's (your DNA is made up of A, T, G, and C) in a row at a specific site on the DNA. Here as an example. I have the deltaF508 and R117H mutations with a 7t allele. My R117H is only expressed mildly because R117H expression is dependent on the intron polyt alleles (the number of T's in a row). There are three variations of this that they check for: 5t, 7t, and 9t. The number corresponds to the number of T's in a row there are. When R117H is paired with a 5t allele and there is another mutations present (like delaF508) the result is "classic" CF. When R117H is paired with a 7t or a 9t and another mutation, the result is a mild or even asymptomatic case of CF. For some reason (I'm not really sure why), the increased number of T's acts as a type of buffer that stops the expression of the R117H.
Here is what I interpret your child's results to be:
-your child has only one copy of the dF508, which was caused by a deletion at exon 10 (this came from either you or mom)
-there is no second mutation present, meaning that your child is a carrier
-they found that your child has a 7t or a 9t alleles, but they aren't sure which; they mainly wanted to make sure it wasn't a 5t
I myself was diagnosed at Mayo Clinic and I have meet their CF team. You will probably hear from some people on this forum that Mayo isn't a CF clinic and as such don't know what they are talking about. I have been a patient there for most of my life and I have full confidence in their teams. If Mayo is saying that your child doesn't have CF, then he probably doesn't. I think the retest at 6 months is a great preventative measure, since as you know there are so many CF mutations and it's difficult to screen for them all at once. The team is probably thinking along the lines of better to retest and have it be the same results, rather then not test again and miss something important. If you want the entire genome sequenced, don't hesitate to call the CF team at Mayo. Even though they may think it's unnecessary, they will do it if you ask for the test to be ordered (though it will be expensive and may not be covered under insurance).
If you do want a second opinion, I highly recommend the Children's Hospitals and Clinics in Minneapolis (if you live in the tri-state area). My cousin goes there and her parents love the staff and team. They are an approved CF center.
I hope all of this helps! Sorry it ended up being so long, but I wanted to make sure I was thorough in my explanation. Please let me know if you have any more questions!
Cheers!
