Hi and welcome Jreed,
Firstly, CONGRATS on your new baby boy! How exciting! I'm so glad to hear he is doing well. Secondly, I'm glad to hear is that your doctors seem to be very on top of the situation (whatever it turns out to be, or not be).
Unfortunately the majority of us with CF are not aware of any family history of CF. Way more often than not, it's a blindside.
I think with one mutation identified, and sweat test of 32, further testing is definitely warranted. I'm a little surprised that they are doing another sweat test as opposed to doing an expended genetic panel. As Ratatosk mentioned, currently there are over 2,000 cystic fibrosis mutations. Newborn screening only screens for the most common ones. For example I have one copy of DF508 (most common), and S945L which is rare and would not be picked up on any basic panel.
As far as being too little for accurate sweat test results... I'm not sure. The test is routinely performed on infants and they have separate parameters of infants below 6 months of age, so I think they account for that. I'm going to be honest with you, I don't have much of "hunch" here on whether or not your little one has CF. You're correct, 32 is just a smidge into the "intermediate" (borderline) range for a newborn. But combined with the one mutation found it makes sense to test further. It may well turn out that he is a just a carrier, but way better safe than sorry. In CF, proactive/preventive treatment is the name of the game with little ones. It is definitely a huge advantage to know very early on if your child has CF so you can do everything possible to maintain their health.
I want to say this to you and mom; I can only imagine the fear you must be feeling, but please try to enjoy your baby and everything that a new baby brings. Cf or no, your baby will be amazing and do amazing things. Really. So just soak it all in. Also, please know this, IF your little one does have CF, the advancements being made in the CF world right now are nothing short of amazing. I'm 36 w/CF and have never seen anything like it, it's exciting for us all. When I was born in 1980 my parents were told I'd be lucky to live into my teens, yet here I sit at 36, a wife, mom, college graduate. I know it's incredible hard to shake the fear of the unknown, but please take heart and just focus on that bouncing baby boy!
Take care and please keep us posted!
Autumn