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P5L

Question
Hello, I have a child with N1303K mutations and P5L, he is 2 years and so far has no symptoms of the disease. Have you heard about this rare mutation P5L? Thank You
Answer
Hello,

Your 2-year-old child has been diagnosed, I suppose, after neonatal screening and has two identified mutations:
- N1303K mutation is considered by experts as a "CF-causing mutation" that is to say causing cystic fibrosis when combined with another "CF-causing mutation". This is a class I mutation responsible for the absence of CFTR protein or chloride channel ;
- the P5L is an extremely rare mutation: it is found neither in the CFTR-France database (which collects the genetic information of patients living in France) nor in the CFTR2 database (more than 40,000 US and overseas patients). It is found only once in the base of Toronto, Canada, associated with the F508del mutation in a 9-year-old patient with a positive sweat test and pancreatic sufficiency (normal secretion of pancreatic enzymes). The molecular genetics laboratory of Brest identified it once several years ago in a child for which they did not have clinical information. Given the nature of this mutation (replacing the amino acid proline by the amino acid lysine at position 5) bioinformatics tools let think that it could be a deleterious mutation (source of malfunction). However, this argument needs to be confirmed by clinical findings observed in a sufficient number of patients for being able to conclude ... or the rarity of the mutation does not allow it.

Moreover, in general, genetic data cannot alone predict the course of the illness in a given individual.
You did not specify the value of sweat chloride (sweat test) performed in your child: positive (> 60 mEq / L), ), negative (under 30mEq / l) or intermediary. You indicate that it has no symptoms if he has a growth in weight and normal height, he has no upper or lower respiratory infections or chronic diarrhea and is pancreatic sufficient (given assay of elastase in the feces) and especially if the sweat test is intermediate, it is likely that it has a moderate cystic fibrosis or dysfunction of the CFTR gene.
In practice, in uncertainty, I recommend your child be followed by a specialized CF Center that will be able to give you the best advice.
Hope this answer can help.
Best wishes
Gilles RAULT, MD, Roscoff CF Center
With the kind contribution of
Marie-Pierre AUDREZET, Molecular Genetics Laboratory, CHU Brest
05.08.2015