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F508del mutation – other mutations possible?
- Question
- Hello,
A gene test my daughter had done returned homozygous F508del (codon507/508-CTT). The test report further says that the MLPA analysis did not show any hint of a deletion of the CFTR gene and that the assumed homozygosity of the above mutation (e.g. as opposed to a compound heterozygosity of F508del and a mutation at the binding site of the primer) could be done in parents' samples.
My question now is: Should we have her tested for further mutations? Which consequences could that have for therapy and who should be tested for what? Parents, child?
Thanks for your effort.
Kind regards. - Answer
- Dear questioner,
I can answer your question as follows:
The F508del mutation is the most common CFTR mutation worldwide and therefore also most often occurs homozygously in CF patients, i.e. in the maternal as well as the paternal CFTR gene. This means that your daughter’s F508del will most probably also be homozygous. However, since for technical/methodical reasons there is a small risk that only the information of one CFTR gene becomes visible, international guidelines recommend to double check the homozygosity diagnosis by an analysis of the parents, who should then be heterozygous.
This means that it would be sensible and advisable for both you and your husband to get tested concerning the F508del mutation. This test has no effect on your daughter’s therapy, but it will affect your further family planning as well as carrier clarification with your siblings and other relatives. If you and your husband are heterozygous carriers of a CFTR mutation, then every further pregnancy bears a 25% risk of the child potentially being affected by CF. If, however, the mutations causing the disease are known in both parents, it would be possible to do reliable prenatal diagnostics and safe clarifications of further family members if you wish to do so.
I hope to have answered your questions to your satisfaction with my explanations.
Kind regards
Prof. Sabina Gallati - 07.09.2010
