Late onset disorders

Dominant disorders may have a late or variable age of onset of
signs and symptoms. People who inherit the defective gene will
be destined to become affected, but may remain asymptomatic
well into adult life. Young adults at risk may not know whether
they have inherited the disorder and be at risk of transmitting
it to their children at the time they are planning their own
families. The possibility of detecting the mutant gene before
symptoms become apparent has important consequences for
conditions such as Huntington disease and myotonic dystrophy.
Predictive genetic testing is considered in chapter 3.