Newborn has 2 mutations-I1366T & DelF508..HELP?


New member
So I received a call that my newborn has two mutations today-I1366T & DelF508. Her IRT was 97.99, and newborn cutoff is 67. I was told that they would refer her for the sweat test at Children's Hospital and I'll be hearing from her Dr and C.H. soon.

*crickets* the MEANTIME, what am I supposed to think? Of course, I googled it and the information I got was "if baby tests positive for 2 mutations, baby most likely has C.F.".

We have 5 children--#3 is a carrier of DelF508. Not sure about 1, 2 and 4. I never got any information after #4's birth so I assume she is not a carrier...

Is it possible that even with two mutations, she won't have it?

Also, is it possible that both me and my husband are carriers and didn't pass it on to any of the other kids, or can pass on just 1 mutation to #3 yet pass on both to #5?

Very concerned and hate having to wait now...any info is much appreciated.


Super Moderator
Dear Mom,
I am so sorry for your worry. I know how hard it is. Let me try to answer our questions.
1) Both you and your husband have 2 cftr genes. Your daughter got one gene from you and one from your husband, so you have one CF mutation and one "normal" one; your husband has one cf mutation and one "normal" one. Each of your children have 25% chance of getting two CF mutation and 50% chance of being a carrier, so possible that only your 5th blessing has both cf mutations.
2) CF mutations are usually considered either 1) disease-causing; 2) unknown whether disease-causing; or 3) disease-causing when with a known disease-causing mutation; 4) not disease causing. df508 is disease causing. I cannot find anything on whether the other mutation is disease-causing, unknown, etc. When you talk to the center to schedule the appointment, I would ask them point blank whether I1366T is known as a disease-causing mutation AND what class mutation it is. They might not tell you. If it were me, I'd ask for the nurse/scheduler whoever to have a doctor call you back so you can ask them before the appointment. They might say no, but I'd still want to know so I can go into the sweat test with more information. Most CF doctors will say the sweat test is the gold standard, but if the mutations are known to be disease-causing will give you some preparation on the likely results. For me, I wanted that.
3) I know how scary this is. The thing that to me is most important to know is that if she does have CF, CF today is so much different than 10 years ago. Our son is 5. There is already a drug that fixes the defect in the mutation for others and one that should be available next year that will help fix his mutation. Not perfect, but there are soooo many drugs in the pipeline that by the time your daughter is 5 there will be even better drugs and eventually (and I mean in the next 20 years) drugs that will cure. I'm sending a big hug and prayers for you and her. Also, below is a link with some details on what to expect at the first appointment.
God Bless


I don't have any helpful information but I can tell you that prayer will definitely ease some anxiety. It was such a shock to my husband and I to find out that our baby has cf. I went to the Internet after being told not to.....big mistake! ! I still Google things and regret it afterwards. Waiting is the worst. You can't change what God has planned for your baby. Enjoy this new baby and try to keep your mind full of positive thoughts!


New member

Thank you so much for your detailed response. What a helpful post.

We called today and got an appt for the sweat test Wednesday (6 days! sigh). My husband asked the lady he talked to about the two mutations together, and after pulling them both up she said that "most often it's not CF." But then of course she said they can't diagnose over the phone, the best way to know is the sweat test, etc. But little is known about I1366T-it is, however, asymptomatic, which I found on a website too.

So could it be possible to have two genes, yet not have CF? I'm not finding much on that--but I would think (in my uneducated, new-to-this brain) that if I1366T is a rare asymptomatic mutation, that maybe them together (DelF508) won't cause CF. I don't know...


New member
I don't have any helpful information but I can tell you that prayer will definitely ease some anxiety..... You can't change what God has planned for your baby. Enjoy this new baby and try to keep your mind full of positive thoughts!

Thank you so much for this! God is good even in the "Even If's" scenarios.