Carrier for CF

Question

Hello,
I (male) have the desire to have children and therefore an azoospermia was diagnosed. Then the genetic test showed I am a carrier for CF that is obviously the reason for this.
In the summer, I have the impression, the heart beats very fast during sport, stress or alcohol exposition. Could this be due to a lack of salt on the blood? Is it recommenden for carriers to increase their salt intake? I will have an appointment for doing a sweat test at the university hospital soon.
Thank you

Answer

Hello,
first of all it is very important, how detailed the genetic investigation of the CFTR-gene has been performed due to the azoospermia. Have only the most frequent mutations been investigated or was a complete sequencing of the gene done? In case only the most frequent mutations have been investigated and only one mutation has been found and therefore you would be a "healthy" carrier, it can be, that a possible second mutation, that is probably rare, has not been found. Therefore a complete sequencing of the gene is necessary.
From the clinical standpoint, you are not a "healthy carrier" as you have an azoospermia, which is frequently due to an aplasia of the vas deferens (CBAVD), which conduct the sperm with the ejaculate from the testicles to the opening of the penis. This is often due to a genetic change, a mutation, in the CFTR gene. Therefore it is very probable, that you have besides the found mutation a second one, which is rare and a "mild" mutation. This mild mutation leads to the CBAVD but not to a real CF; we call this a CFTR-associated disease.
To find this out, a sweat test is mandatory and the complete sequencing of the CFTR gene.
The sweat test has to be done at a certified CF-center with a pilocarpine ionotophoresis as method, measurement of the conductivity, like many hospitals offer, is not sufficient.
In case the sweat test is pathologic, concentration of chloride is over 60 mmol/l, which is not very probable in this case, one could make the diagnosis of CF. In this case a second mutation will for sure be found and you would have more symptoms than just CBAVD. As you do not report any lung symptoms, this would be very improbable and it would be more a "mild" form of CF.
In case the sweat test has results between 30 and 60 mmol/l chloride concentration, it is in the borderline range. Than it would be typical to find a second, more rare and very mild CF mutation in the CFTR-gene, which causes not a "classical CF" but a CFTR-associated disease with CBAVD. Such patients should regularly be seen in longer time-intervals in a CF center, as the sweat test value can increase by time and can turn to a "mild form of CF". This is dependent on the concrete mutations found.
In case the sweat test is below 30 mmol/l chloride concentration, it is in the normal range. In case really no second mutation is found a "healthy carrier" status is possible, but the azoospermia would be due to other reasons (is there really a aplasia of the vas deferens? This can be seen in the ultrasound). It is also possible to find a second mutation, however the sweat test ist normal. In this case it has to be controlled in longer time intervals, how the value is changing, because there are two underlying mutation.
6% of the population are "healthy carriers" and have indeed only one mutation, the healthy gene is sufficient not to be ill. These people do not have to be checked regularly and do normally not have an azoospermia. Healthy carriers can have more frequent problems with the upper airways, the rule is however, that they do not have any symptoms and do not know anything about their carrier state.
Therefore:
1) have a complete sequencing of the CFTR-gene done
2) have a sweat test done in a certified CF-center
3) According to the findings further diagnostics: microbiology of the upper airways, lung function testing, elastase in the stool, blood values, x-ray of the lungs.
Then making a diagnosis with the consequence it it is necessary to be seen regularly in a CF center, or not.
A lack of salt in the blood will only occur, if the loss of salt via the sweat is high; this is not the case in a healthy carrier, but if sweat values are in the upper borderline range, the loss of salt via the sweat is increased. Such a marked loss of salt that it could influence the heart can nearly be excluded - this is not even seen regularly in patients with a "severe CF" who have sweat test values over 100 mmol/l.
Best regards,
Daniela d'Alquen

20.01.2026