Negative sweat chloride, cf still possible?

[Mommaschulz4]

Hello! I have joined this group because I’m trying to get some ideas on what could be going on with my two year old. Warning: this may be a long explanation
He was born with gastroschisis (intestines outside of his body) at 37wks, and was 3lbs 6oz. He has struggled to gain weight and Has almost never been on the growth chart. He now has a gtube that gives him most of his nutrition. There is no reason for him to
Not be able to eat and gain weight, and they don’t know why he was so tiny. He has been delayed in a lot of areas due to being in and out of the hospital his whole life between vomiting and tummy issues, to needing oxygen for every virus that hit him. He’s not diagnosed with asthma but they treat him as such. He has ear tubes from numerous ear infections, has had two gtube surgeries, and recently had his tonsils/adenoids removed to help with sleep apnea. He has a chronic cough. He’s had pneumonia 3 times in his life. He’s had RSV 3 times. He is only 2 and 1/2 years old, and he’s in 18-24 month clothing and has been for almost a year. I’ve looked up every lung issue that he could possibly have and the only thing that makes a little sense is cf, or an immunodeficiency to explain why he gets sick so easily and so severely with such simple virus’. We have done a sweat chloride test and it was negative. I’m asking his geneticist about cf genetic testing and he sees an immunologist in March. Has anyone ever been positive for cf in genetic testing with a negative sweat chloride? Does this sound like it could be cf? I know there is something Underlying and Whatever it is, I want to do whatever is best for him as soon as possible.
Thanks so much for any advice!

 

[kenna2]

To me this doesn't sound like CF but more of an immune issue. I know with small children, it's really easy and really common to get RSV which can lead to pneumonia. They're all viral and that's hard to avoid, but both which usually require hydration and oxygen even in adults. CF patients are diagnosed mainly based on their sweat chloride test due to our salty skin so a negative test is pretty accurate.

 

[Ratatosk]

When you say sweat test was negative, what were the numbers, how old was he at the time and was it done at a cf facility? What do his stools look like? Are they normal, greasy, floating, frequent, bulky...? Was he tested via newborn screening for cf?

 

[Mommaschulz4]

He got 19 and 11, it was done at the children’s hospital lab, so I’m not sure? He was 2 when it was done. They have been bulky, but he also goes through periods of diarrhea. He rarely has normal healthy stools. I’m honestly not sure if he was tested as a newborn? I should mention, he did not get pneumonia from RSV each time, and he’s been hospitalized a good 20-30 times in his life needing oxygen for whatever reason, generally wit a virus or cold of some sort, and they don’t really know why, but they’d say his lungs rarely sound wheezy, just more coarse and crackly. And his sister has the same issues, just not to his extreme. We chalked it up to a gluten/wheat allergy with her tummy issues, and they said she has asthma. But she just got pneumonia and now I’m wondering if there isn’t something else going on with her because she has a constant brutal wet cough as well. But who knows, I could be paranoid lol

 

[kenna2]

19 and 11 are way too low for CF. 40-60 would be considered borderline. I'm so sorry you're struggling with all this. I can't imagine how frustrating this must be for you.

 

[Mommaschulz4]

I do understand that is significantly low, but I have read about families with negative sweat chloride who still ended up with positive genetic testing, even if considered a mild form. I would love to at least rule it out because it is one of the only few things that makes sense with all he has been through this far. But thank you! I’m in the process of trying to get the testing, so we will see if it goes through or not. I’m also waiting for an immunology appt. so maybe I will get some answers for him there. I appreciate any input and/or advice though!

 

[Ratatosk]

The reason I asked about stools and the sweat test numbers is because maybe you could ask if they could do a fecal fat test to test for pancreatic insufficiency.

DS had a sweat test at 3 weeks and it was 32; however, he was a very teeny tiny baby and sweat tests at that age if low, weren't always accurate because as he got older, he was very salty. Your child was older when tested.

 

[Mommaschulz4]

I have been checking out his stools much more recently because I don’t really
Know what people mean by oily and greasy, but he has lots of stools that are more on the slimy side that when he wore diapers, would soak into the diapers quite a bit, but I’m not sure if that’s what you mean. I will mention it to his pediatrician and see what she thinks. But I’ve decided to wait it out on a few appts (immunology, pulmonology), to see if we can get answers that are not cf related first before pushing for genetic testing. But I’m otherwise at a loss, so hoping for some answers to best know how to help him! Thanks for the input!

 

[Ratatosk]

If ds doesn't take enough enzymes (creon) his stools are not well formed, break apart easily when I flush and leave a residue at the waterline, float or "stinkers not sinkers". He also would stool frequently, not just once or twice a day, but every few hours if not more. Sometimes his stools would be yellowish with green flecks or orangish. I didn't see a normal brown, well formed poo until we got his digestive issues figured out.

 

[emason]

My son has low sweats and 2 mutations. His diagnosis is CRMS though and not CF since his sweat is so low. While it is possible to have the genetics even with a negative sweat, USUALLY (and there are always some exceptions but almost always) a sweat that low wouldn't be associated with pancreatic insufficiency - which is what causes the classic Failure to Thrive in CF kids. Most kids with low sweats have residual cftr function and remain pancreatic sufficient. So they would not have the same issues with weight/growth commonly related to CF. I would think it's very unlikely that his GI issues are related to Cystic Fibrosis. I don't think genetics to rule things out in the presence of symptoms are ever a bad idea so I wouldn't dissuade you from the genetics testing to be sure of course but I would think there is another cause out there personally.

 

[ddawson]

Has Primary Ciliary Dyskinesia been considered? My son has this (I am on this forum because it's so rare that the only management available for it is based on CF management). PCD is often missed/misdiagnosed- his pulmonologist says it's probably more common than CF, but it's rarely diagnosed.

 

[Mommaschulz4]

I have never heard of this, but I will definitely look into it. My son just saw his pulmonologist yesterday and he ordered a bronchoscopy for next Friday and he gave the okay for genetics to do cf testing and immunology is doing a blood work up as well.
Do you know how it’s diagnosed and what all the symptoms are? Thanks for commenting btw!

 

[Mommaschulz4]

Thanks for the input. Did you have the full ambry panel workup? The pulmonoligist agreed it’d be a good idea just to rule it out since we are running out of ideas.

 

[ddawson]

Usually symptoms like chronic wet cough, runny nose, frequent infections (especially ear infections in younger children), frequent pneumonia, unidentified respiratory distress after birth, etc, (often people who they thought had CF but tested negative, or even misdiagnosed with asthma) will often prompt them to test for PCD. My son has Situs Inversus (mirrored internal anatomy) which they found when he was born. 50% of people with PCD have Situs Inversus, so they suspected his very early.

A diagnosis will come from a biopsy (nasal or lungs) looking at the ciliary structure, and/or positive genetics tests. Unfortunately, both of these could potentially come back negative, and someone could still have PCD. PCD can be caused by abnormal ciliary structure, inability of ciliary to "beat" properly, or a combo of both. A biopsy would only show structural abnormalities. And even if genetics tests are negative, not all the genes that cause PCD have been identified.

It's definitely worth looking into. His respiratory symptoms seem very similar to many PCD cases. And if it is, it's always best to catch it early!

 

[Mommaschulz4]

Thank you for all the information! Hopefully they will do a biopsy when they do his bronchoscopy on Friday so we can figure it all out. I’ll let you know if they figure it out though. He also has the genetic testing for Cf done the same day.
I also just discovered today that he has no antibodies for pneumococcal so he had to get a vaccine to see if it helps, and if not, that could be part of why he is so often sick. So we are finally getting some answers soon hopefully!

 

[Mommaschulz4]

Nasal biopsy came back negative for PCD but we are still waiting for genetic testing for cf to come back.

 

[Mommaschulz4]

Genetic testing is negative. On to trying to figure out our next step to get a diagnosis! Thanks for all the help and input.

 

[Kristan]

Hi,

I have PCD that was diagnosed a few years ago at 49. Not sure what genetic testing was done, but thought I would mention my nasal biopsy done 20 years ago came back structurally normal even though I had it. Pneumonia, ear infections, and sinusitis was very common for me in childhood and I had a negative CF sweat test. I am assuming that the doctors have checked on acid reflux/ aspiration issues as a possibility. If the issues are stemming from the clearance on mucus then you may be interested in contacting one the following clinics that are participating in the GDMCC. They may have ideas or be able to look at the information differently.
https://www.rarediseasesnetwork.org/cms/gdmcc

 

[Mommaschulz4]

Wow, this is super interesting. He had genetic testing for cf after much pushing but I didn’t get him genetically tested for pcd. Maybe I should continue to push for that as well, if we don’t get answers with some
Labs I’m waiting on. He does have reflux, but does not aspirate. He has the multiple ear infections and has had pneumonia 3 times in his life and is 2. I’m
Not sure he’s been diagnosed with sinutis though? But thank you! I’ll definitely look further into this.

 

[ddawson]

Yes, biopsies often come back negative for PCD when, in fact, the person has PCD. Ciliary structures can be intact, but are still dysfunctional in their mobility. Also, ciliary biopsies are very difficult to do well- sometimes that can come back negatively just because they were not done correctly. Genetic testing for PCD can come back positively, negatively, or inconclusively (because not all PCD causing genes are known). Still worth pushing for, genetically.

There is also a strong correlation between reflux and PCD. There's a study that found that 3/5 kids with PCD also had reflux that continued on to adulthood.

Sinus cavities (except for the ones behind the cheeks and between the eyes) won't start developing until kids are 5 years old and then again at around 7 or 8, so he may not have sinus troubles yet.