Please note: While some information will still be current in a year, other information may already be out of date in three months time. If you are in any doubt, please feel free to ask.

query - carrier

Dear Sirs

I sent a question to the cystic fibrosis organisation and they directed me onto you as it was medical question. I have just found out that myself and my sister are carriers of the cystic fibrosis gene only and do not actually have it. I wanted to know if it was true that if you are a carrier you can also show some slight symptoms of CF with lung problems etc? My sister has severe asthma (COPD) and i have asthma also and always cough a lot and have a lot of flem/mucus (sticky gunky) that comes up. Sorry to be graphic. I have read a lot of places and forums online where people say that you can have symptoms or slight symptoms show and some sites say no. I also read some scientific facts somewhere that there is more and more evidence showing this with patients coming forward? I would be very greatful if you would be able to help me with this matter?
Dear questioner,
Let me provide you with some information, that was already given by two answers from Dr. Hubert and Prof. DeBoeck:
“Carriers of a CF mutation are in general healthy. Being a carrier of a CF mutation does not cause the disease, because CF is a disease that only manifests itself when you have two CF mutations, one on the gene inherited from the father and one on the gene inherited from the mother. However there is some data that suggest that minor respiratory problems or ENT problems (such as rhino-sinusitis, nasal polyps) might be a little more frequent in healthy carriers:
A few studies have been conducted on parents of children with cystic fibrosis, also known as "obligate heterozygotes" because they carry a mutation in the cystic fibrosis gene (or CFTR gene).
In 1988, even before the discovery of the gene, Byard et al compared 280 parents of children with CF (obligate heterozygotes) to 280 non-carriers parents (parents of children with heart disease). "Healthy carriers" parents complained of wheezing more often but their lung function was comparable to that of parents with no children with CF.
In 2001, Castellani et al. compared 261 obligate heterozygotes to 201 controls, looking in particular for respiratory, digestive or ENT diseases. They found a slight increase in blood pressure in heterozygotes, as well as nasal polyps in heterozygote men. However the differences between the two groups disappeared when age was taken into account.
In 2005, Dr. Isabelle Sermet showed that the functioning of the CFTR protein was decreased in 52 parents of children with CF. In particular, their average concentration of chloride in the sweat test was higher than that of non-heterozygous subjects, but much lower than that of patients with CF. Among them, three complained of chronic sinusitis and 2 of asthma.
A study also published in 2005 (Wang et al) found that 36% of obligate heterozygotes (53/147) had chronic rhino-sinusitis based on their response to a self-administered questionnaire. A more detailed ENT examination confirmed the reliability of the questionnaire.
In summary, based on current knowledge, the parents of children with CF are generally well and deserve their name of "healthy carriers" even if the functioning of their CFTR protein is reduced. They are not at risk of developing severe respiratory impairment. However, small respiratory or ENT symptoms might be a little more frequent.

Of course, being a carrier of a CF mutation is no guarantee that you will be healthy. A carrier of a CF mutation may have medical problems that need proper diagnosis and treatment.
Moreover, if a carrier has CF suggestive symptoms, (e.g. chronic respiratory infections by specific bacteria, inflammation of the pancreas, male infertility) it is justified to achieve a complete genetic analysis in search of a second mutation in the CFTR gene, which would then indicate a mild form of cystic fibrosis. In that case, the person of question has not been a healthy carrier as indeed two mutations were underlying that could not have been detected at the beginning.”
Dr. Daniela d’Alquen (Coordinator of the Central English Archive of ECORN-CF)
The answer is edited by: Prof Judy Bradley