However, the severity of some hereditary disorders is difficult to predict. This is particularly true of dominant hereditary genetic mutations, because it is extremely difficult to determine whether they will be transmitted, even if a screening test is carried out. Neurofibromatosis is a good example.
不過，有些遺傳疾病的嚴重度難以預知，特別是顯性遺傳的基因變化更大，即使經過篩檢，留或不留仍是千萬難，其中神經性纖維瘤就是一個最好的例子。