Symptoms in healthy carriers?

Question

Hello,
At time of diagnosis, I was told that healthy carriers showed no symptoms. After meeting other parents of children with CF, I realize that many of us have chronic respiratory or digestive problems (asthma in my case). But I don't know if these observations are representative of all parents.
I wondered if a study was conducted on the subject.
That is a question I have been asking myself regarding the brothers and sisters as we do not know if they are carriers of one mutation or not.
Thank you in advance for your answer.

Answer

Hello,
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. In the case of more disabling respiratory symptoms, 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.
Best regards.
Dr Dominique Hubert

10.11.2011