The severity of neurofibromatosis depends on the type of a second mutation of the pathogenic gene, and genetic mutations are extremely complex, so that gene sequencing allows doctors to determine the location of the mutation in only 50 % of cases. This makes it very difficult to predict how serious the condition will be.
由於神經纖維瘤的嚴重度取決於致病基因第二次突變的類型，但基因突變型非常複雜，能以基因定序的方法找出突變處的機率只有一半，因而難以預知其嚴重度。