Any negative sweat tests and two different CF mutations?

Laura - posted on 11/20/2009 ( 14 moms have responded )

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We have identical twin boys with CF that are now 6 months old. They have the F508 and D115 mutations. They passed the sweat test, not even borderline. Our pulminologist even said they were considering lowering the borderline results for infants and these guys still don't fit into that and would still be normal sweat tests. They don't need enzymes and their lungs sounded fine.



I am hoping that the negative sweat test means that we won't have any of the serious problems down the road. Any one have any experience with this?

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Mandy - posted on 10/19/2011

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We have had two negative sweat test, but with the problems we have every doctor my daughter has seen ask if there is CF in the family (and their is). We are now in a really bad bout of bronchitis/pneumonia/respiratory inflammatory disease and can not seem to get it under control. I am starting to wonder if her sweat test was not correct.

Christy - posted on 12/29/2009

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We never searched further for the name of the 2nd mutation because the first test incorrectly cost us $5000 and insurance didn't pay! It was supposed to cost $250. I think there are many thousands of mutations and the panel test we did was only for the 90 most common ones. There are many many more unknown ones that are rare and some of those are less severe, which is what we assumed for my husband. He has an intact Vas deferens, which is the problem with most CF boys, but we had other infertility issues. Our son was our blessing from God with no assistance needed in getting pregnant. We do worry for our son's fertility though since he has the 2 common mutations and I believe 85% with the double Delta F 508 have the vas deferens issue.

Christy - posted on 12/26/2009

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My son has CF diagnosed on the newborn screen with a positive sweat test and subsequent genetic test (double Delta F508). He's now 3 and doing well. At the time he was diagnosed, we had our daughter tested and she was negative on the sweat test. My husband was 41 at the time and had a history of pneumonia as a child, asthma as an adult and GI problems more as an adult. We had him do a sweat test and it was positive twice. We then did the genetic test for the common mutations and he was positive for 1 Delta F508 and no other common mutation. He likely has a lesser 2nd mutation that we haven't determined (and our insurance did not cover the expensive genetic testing). So the good news for us was that my husband's lesser mutation had really not caused him much problems with him being 41 and fairly healthy. We're still wondering if our daughter may have the milder 2nd gene and is just sweat test negative. She has some GI issues that are mild. We're just waiting and not doing further testing for now.

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Kristale - posted on 10/28/2013

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Please let me know what u found out. I have a two year old having the same problems. All blood work show signs show she does other then wanting the DNA work and the sweat test showed low levels but all the signs r there

Elaine - posted on 08/03/2013

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I believe that even if the F508 comes out positive... it's just positive that they are a carrier of the mutation gene. Further test (like the sweat test) will determine if they have the actual disease. Being a carrier of a mutation means you just carry the mutation.... not the actual disease but it's good to know so your when children become adults can have their significant other get test for the mutation , when they decide to have kids of their own. If both mom and dad are carriers of the mutation , then there is a 25% chance the child will carry the actual disease or just pass on the mutation .

Bek - posted on 07/15/2013

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If anyone still reads this please email me bekablank@yahoo.com cause our 8 yr old daughter has been very sick, digestive issues, lost lower left lobe lung , pancreatic attacks, anorexic cause can't get her to gain. We did sweat test last yr was negative Dr said felt false so re scheduled her for one tomorrow. Can a kid have CF if pass sweat test? I'm so confused

Gillian - posted on 01/30/2012

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yes, same thing happened to my daughter when she was very small, but she had digestive issues almost from the start and that is why we pursued diagnosis of her issues. The negative sweat test actually though off the proper diagnosis for a while. She didn't need any lung treatments until she was a lot older than most kids with cf. Just know what to look for and stay on top of their nutrition and clear lungs at this age and hopefully their mild version of cf will stay that way(it's certainly been known to happen).

Laura - posted on 10/25/2011

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Yea, we don't understand much more but do our quarterly appointments. I am supposed to have the boys in for their yearly which will redo all the big tests. We already had the chest xray and the doctor wants to take a second look at the dvd :( We have to redo bloodwork and the sweat test - also no fun!! Their stool came back all pancreatic sufficient.

So the sweat test results I will come back and post once I get the insurance and appointment set. We joined a study that tries to find why the symptoms are so different even in siblings with the same genes.

I don't think the sweat tests is very accurate, I think it's just one of many defects that show with CF and It seems like you can have some problems but not others. I can't remember the gene mutation that has a medicine that treats the defect directly but we are certainly getting there for all of the mutations some day. We are still really lucky with our twins, they do the airway clearence 2x day 30 minutes each time and we are happy that is all.

Deirdre - posted on 10/25/2011

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I have seen a few people in different CF boards post that their kids have had at least one negative sweat chloride, but still have 2 mutations. I hope for your sake this means your children have a "mild" case. CF is so weird and scary! My son, Blake, is almost 2 and has 2 copies of d F508m but has been VERY healthy (knock on wood) thus far. I heard of people who are only carriers that seem to have more complications that he has had so far. The hard thing is that they are discovering new mutations all the time, so there may be people who do have CF, but only 1 mutation can be identified. I believe the count of identified mutations is up to 1500 or so!!

Jamie - posted on 12/28/2009

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Wow thats great he didn't get that sick,and he was able to have kids i was worried that my baby doesn't even have a chance to have kids even though hes only 3 months i still think about it and get sad so that gives me hope.Do you know the name of the other mutation?My baby has the common one and i forget the other but i'm gonna ask the doctor.Well take care and please if you know the name please let me know

Jamie - posted on 12/18/2009

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Thank you!Aw your boys are adorable! It seems like we are going through the same thing almost. Ya they said he has the two genes that's why they're not in a hurry to do the sweat test.He also has the common one and i cant remember the other.He is doing really good, about a week ago we had took him to Pittsburgh for the CF and he weighed 13.2 lbs,but he also weighed 8.1 at birth,Sept.23.We have to go every 2 months,it was every 2 weeks.Do you have to do the percussion on them?They told us to do it on him even though he doesn't need it just to get him and us used to it.I feel so bad because i haven't really been doing it as much as im supposed to.He cries when i do it unless hes asleep.Well let me know how they are i'm not used to this circle of moms,how it works, but you can leave me a message on my page or on here.Take care

Laura - posted on 12/17/2009

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They did pass their sweat test. I don't remember their numbers, but I do recall they were well into the normal results, not even close to border line. They know they have CF by their blood work. This disease needs two mutated genes to have CF. Anyone with the two genes has the disease. There are SO many genes to test for it is hard to confirm CF this way. Basically your body has these two genes or "instruction manuals" for telling your body what to do. If you have a good gene, you can't have CF and your body knows to listen to the good gene. With two mutated genes, your body doesn't have a good gene to listen to.

The good news: our boys have a really bad gene and a really mild gene. That is how they passed their sweat test. They don't need enzymes. They did have milconium illius (something about passing hard stool after the first 24hrs of birth). Other then that we just are following up with Boston Childrens hospital (Dr. Haver) every 3 months to be sure we are good since it is such a serious disease. I would recommend pushing for a sweat test and the genetic testing to be safe. It sounds like even if they did have it you would be in our shoes. We are in a gray area and can only hope that we won't have to fight this disease. The great point is that there is so much movement towards a cure if they ever have symptoms we should be able to fix it.

Gaining weight is the best sign that you don't have to worry about the enzymes (they are a pain to do every feeding!!) Our boys are 13 lbs and 7 1/2 months. They were 3 months premature so they are on target for their corrective age of 4 1/2 months.

We keep getting told that this affects each person differently and that anything can happen. At least getting all your information like knowing what gene mutations your son carries. Ours have delta 508 and a d 115 mutation. The 508 is the common one and usually shows more severe lung disease. The blood test is over $7k so make sure you get your insurance company on board before you do anything!!! I have also heard that a lot of places diagnose early to be safe.

The hard part is even if the blood test shows that he doesn't have 2 mutations; there is always a risk that they just haven't discovered or didn't test for all the thousands of different mutations.

It is very complicated, just take one step at a time and don't rush. You have a healthy growing son you are doing amazing already.

Jamie - posted on 12/17/2009

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My 12 week old baby has cf and they had put him on enzymes and then said he didn't need them and took him off. They said he's doing really good hes not having any problems and he's gaining alot of weight.The doctor said shes not even worried about doing the sweat test because she knows he has it.Are your babies growing good?I dont understand,if they passed the sweat test i thought that means they don't have it.I still don't know to much about it.Please let me know how they're doing and if you can answer my questions.I know i didn't help you but i wanted to know because i don't understand if they past.Thank you.

Katie - posted on 12/05/2009

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Hi! My daughter was not sweat tested til 2 yrs old and they did 3 different tests. The first was 81, the second was 63, and the third was 38. They did not believe she had CF. They said she would not have had a negative one if she had CF. Well, obviously they were wrong. Other reasons was that the first gene test only showed 1 gene Delta F508 and so they said she was just a carrier. Later a further test showed she carried a gene that's only been identified in 1 other person. Crazy. Also, her poop tests showed she was absorbing her fats therefor she was pancreatic sufficient and they said that's rare but still possible. It took me taking her to another CF center for them to do a throat culture and found out she grew pseudomonas and said she had to have CF to grow that. Anyways, 5 yrs later she has done pretty well. Only 1 hospitalization for polup removal combined with a tune up. That was when she was 5. We just recently found out from another test they do for pancreatic stuff that she was actually insufficient and just started enzymes a few months ago. They had to put her to sleep and go down in her through the mouth to stimulate the pancreas. They said they don't normally do it since it's kind of invasive but since they had to go in there anyways for another procedure they said they would do that also. My daughter's lungs almost always sound fine. She had a mild case on pnemonia when she was 10 months old. CF is so complicated! 5 yrs later and I'm still confused lol. Can't tell you for sure if a neg sweat test means less complications but it definitely can't hurt to hope. That's all we can do.

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