Many of the diseases that occur in young adults have an underlying genetic susceptibility. 

In many instances genetic susceptibility factors are present in other family members who might have no signs of the condition but are at risk of developing the disease. 

A genetic diagnosis in an affected family member can allow others in the family to access testing to determine their status.

Often DNA testing may be sought by members of the extended family. It can clarify the risk to children and open up reproductive genetic options to assist future offspring.

 Many adults with childhood genetic disorders may require specialist genetic consultation for clinical advice at key times, such as during adolescence, planning a family or during illness.