When No One Has Had the Disease
Since one copy of an altered CF gene does not cause symptoms, this copy can be passed down to family members without any impact on their health. Unless they have a child with CF, most people who carry an altered CF gene do not know they carry it. Once parents have a child with CF, all of their children should be tested for CF. Other relatives, such as brothers, sisters or cousins, have a chance of being CF carriers and might want to have carrier testing.