CF excluded but a mutation R117H

Question

Dear ladies and gentlemen,
I am 33 years old with CF, my daughter is 7 years old with CF and my son is 14 years old. To him, a CF had been excluded via potential difference/ molecular genetic / sweat test in two different hospitals. But my son ought to be affected by a not-known mutation and he carries the mutation R117H.
My son is 154 cm heigh and weighs only 34 kg and he looks like a CF child.
He has asthma, reflux, dysthrophy, fructose intolerance, hypothyreosis, IgA deficiency. One time in 2003 Pseudomonas Aeruginosa.
My question, a last possibility that comes into question, at a urologist one could have made an investigation but I do not know at what age that could be the case as he does not look like 14 years old and if he is sterile, because then he must after all have CF.
The health condition is very critical and here nobody helps my son which I regret very much.
Yours sincerely,

Answer

Dear questioner,
your concern, that not only you and your daughter but also your son might suffer from CF, is understandable.
In your specific case, in which you have as a CF patient a daughter with CF, the question if your son suffers also from CF can only be adressed if your two mutations and the mutation of your partner as well as the mutations of your daughter are named.
However I think that if an extended CF diagnostic (measurement of the potential difference, genetic testing and sweat test) has already been done in two hospitals specialized for CF, and both hospitals came to the same result, CF can be excluded with a probability boardering on certainity.
Your assumption, that your son, in case he is sterile, automatically suffers from CF, is not right. The ascertainment of sterility due to an urologic investigation does not assure the diagnosis of CF, as other illnesses may be accompanied by sterility respectively CF males may be fertile.
In case there is a special kind of sterility namely a so-called obstructive azoospermia (1-5% of all sterile men), about 30% of those men carry a R117H mutation (mostly with T7 association). Therefore an investigation of the sperm of your son makes sense, however that does not mean that he automatically suffers from CF, but rahter a CFTR (chloride channel) caused disorder. However a spermiogram is only possible after passed puberty.
The diagnoses, that has been made to your son (asthma, reflux, fructose intolerance, hypothyreosis) are all today well treatable and should not be the cause for dystrophy. There are however a row of other reasons for dystrophy, which you should let be excluded by your pediatrician. Also a temporary colonization with Pseudomonas aeruginosa is found in humans not suffering from CF.
In any case I would recommend a genetic counselling to you.
I whish you and your family all the best,
Silke van Konigsbruggen

26.05.2009