My (very limitted) understanding is that whilst there is no cure, there are treatments and therapies that can help slow down the progression of the disease.
If you catch the disease very early and can halt or dramatically slow down the progression then there is a chance the person can lead a nearly normal life. It may even be medicines can be developed to reserve small amounts of damage that aren't effective on later diagnosed patients with much more severe symptoms.
Part of the problem with slow progression diseases is that research into possible preventative medicines (like asprin for heart disease/stroke) takes a very very long time to detect meaningful results. A more sensitive means to track deterioration may help speed up those investigations even if it isn't 100% accurate.