Perfect prognosis

Hmm, what if we could make a perfect prognosis for someone from birth, based on any genetic diseases. So, a child could be told "at 24 you will develop a neuro-degenerative disease, meaning you will not be able to use your arms. By 28 this will spread to your legs and at 32 you will be in a coma."

Obviously this is a thought experiment, so please engage it as such.

Should the child be told? Would they be? We are only formally told about puberty at about the time that it happens (at least in my school). Is that a parallel that we can take? It is something you have general notions of, and society being what it is you have general expectations for something like it. Of course, mainstream  TV/media and the availability of porn mean that most of those expectations will be wrong.

The parallel is also different because it is a norm expected of everyone. Give or take, children enter puberty at around the same time. Women enter menopause around the same time plus/minus a decade. All stasticially expressible.

But what if someone had a prognosis to die or comatose by the time they were 30. How would that shape their upbringing? The parents would know they would have to plan the funeral, the children would know that if they had children (even at 16), they would not be able to care for them all through their formative years. It would create completely different expectations for life.