Genetic counselling after carrier detection by newborn screening when one parent carries ΔF508 and the other R117H

Newborn screening (NBS) for cystic fibrosis (CF) has been carried out in Victoria, Australia since 1989. The primary screen is immunoreactive trypsinogen (IRT) followed by DeltaF508 mutation analysis. As part of this process, carrier babies are detected and their parents are routinely offered carrier testing as part of their follow up. The DeltaF508 parent is identified and the other parent has an extended mutation analysis performed in case they are also a carrier. One of the mutations in the extended analysis is R117H which is associated with a broad phenotypic range, from CF with suppurative lung disease, to no clinical disease. We present four healthy DeltaF508 carrier babies identified by our NBS service with both parents identified as carriers, one DeltaF508 and the other R117H. Owing to the variable phenotype associated with R117H we have developed an approach to this difficult genetic counselling situation. Centres offering or considering NBS for CF will need an approach to this problem.