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Moderate forms

My son 9 months old, has moderate form cystic fibrosis F508 / R347H. He is to this day without symptoms, without pancreatic involvement.
I do not understand the term "mild" since I am told that this can evolve into a classic form like staying moderate. Do moderate forms have a somewhat greater life expectancy?
Given the form he has, does he have a chance of remaining asymptomatic until adulthood? Can this disease remain silent for several years and degrade rapidly thereafter? It is difficult to find patients with the same genes.

The diagnosis of cystic fibrosis can be made even in the absence of clinical symptoms especially in the case of positive neonatal screening:
 - If the sweat test, performed under the required conditions in a qualified center, is clearly positive, ie measuring a concentration of salt (sodium chloride) in sweat greater than or equal to 60 mEq/L
 - AND / OR if the child's blood sample made it possible to identify 2 mutations of the CFTR gene known as causes of the disease (so-called "causing CF").
The combination of the two mutations F508del and R347H is among the combinations causing cystic fibrosis. However:
 - The F508del, a class II mutation, induces the synthesis of a CFTR protein which is destroyed before it reaches the membrane of the cell: it can not therefore function as a chlorine channel;
 - The R347H is a mutation of class IV considered as "mild". This mutation leads to the synthesis of a protein that can migrate to the membrane of the cell and permit the passage of chloride at a rate that is less than normal (the conductance of the channel is diminished).

CFTR2, the largest international database that collects genetic and clinical information from people with cystic fibrosis, reports 137 individuals who associate this "mild" mutation with another "causing CF" mutation. These people usually have an attenuated expression of the disease with especially the most often exocrine pancreatic sufficiency.
This statistical information however, does not allow to predict completely the disease evolution for a given individual because other factors than the CFTR genotype (the combination of the two mutations) can influence the phenotype (evolution) : environmental factors (pollution, lifestyle) or genetic factors related to the influence of so-called modifying genes that can alleviate or accentuate symptoms due to chloride channel dysfunction. A large-scale international study currently underway aims to identify these modifying genes from a blood sample.

To answer your questions:
 - Yes, your child may remain asymptomatic until adulthood, but it is impossible to state or indicate the probability;
 - Yes, the disease can remain silent for a longer or shorter period before manifesting itself, which does not mean that it will deteriorate very quickly.

The uncertainty regarding the evolution of the disease warrants a regular medical follow-up in a specialized CF Center eventhough it can be spaced according to the situation. The care team can answer your and your child's questions.Finally, I repeat some advice:
 - To lead a life as normal as possible: like all children, go to school, have physical activity, play sports according to their tastes and aptitudes, play with their classmates, go on holiday;
 - To respect the general rules of hygiene of life, in particular to avoid the polluted atmospheres in particular tobacco, to ensure a good hydration;
 - To Follow prescribed treatments and time for care;
 - To Trust in the future: therapeutic advances are constantly evolving and increasing rapidly.

Hope this answer can help.
Best wishes
Gilles RAULT, MD, Roscoff CF Center